Deep Sky Astrophotography

[jrista]

Well that looks terrific!!Howcome you're not using a refractor telescope instead of a photographic lens?It doesn't look that your budget is very limited as that lens probably costs a lot more than most refractors.And another thing I was wondering...has anyone in here had any experience with a sony sensor dslr?We know at 400 iso and below it is better than the canons but at 800 or 1600?Is there something to be gained by using one?

My lens is actually better than many refractors. It also has a significantly larger aperture than most refractors, and aperture is critical in AP. Bigger photon bucket. To get a comparable refractor, I'd need to spend about $7k or so anyway, and the aperture would actually be smaller. To get a refractor with a similar aperture, I'd need to spend about $11k (there are not many 150mm aperture refractors out there...the TEC140 has a 140mm aperture and is about $6000 (and with necessary accessories, a bit more), and there is the Officina Stellare HiperAPO 150mm, which is almost $11k). So I wouldn't have saved much with a "real" refractor.

There are other benefits with the Canon lens. The Fluorite elements. The nanocoatings (no current refractor uses nanocoatings yet, but it's actually a big deal for transmission) on the internal elements. The corner-to-corner field and color correction. There are a lot of things about the Canon superteles that actually blow many telescopes out of the water. Hence the reason I use it as my telescope.

Regarding Sony cameras. Sony's sensors are fantastic, and actually the companies ZWO and QHY are working on putting the Sony 36.7mp full frame sensor into dedicated, cooled and regulated astro camera bodies. So soon here, we will have the ability to run the same sensor as the D810 in a camera body that can cool the sensor 45 degrees C below ambient. That will make for one hell of an astrocamera. DSLRs won't be able to touch it.

Sony CAMERAS, on the other hand, are not actually that good for astro. It isn't because of the sensor, it's because of the hard-coded processing that the BIONZ X chips do. They force spatial filtering on all exposures longer than 30 seconds, and since most astro exposures are several minutes at least, that causes problems. For astro, you want the purest data you can get, that has been screwed with the least, for maximum linearity and detail. Sony has been slowly improving things, but until they disable the forced spatial filtering for exposures longer than 30 seconds, i don't recommend them for astro.

For astro with a DSLR in general, I recommend ISO 1600. That gives you a good balance of low read noise (on cameras that use Sony sensors, often as little as 2e- or less!) and decent dynamic range. You can use shorter exposures as well, which can allow you to maximize resolution and avoids problems with poor tracking that most low end German Equatorial mounts have. It's best for beginners, but even advanced imagers will usually use shorter exposures these days.

 

[jrista]

Didn't you move to a dedicated astro-cam recently?? Or did I get that wrong?

Anyway, as usual your post are really really helpful, greatly appreciated.

Sebastian

I did. This is an old photo from a couple years ago. I am currently using this camera, the ASI1600, and filter wheel, the Atik EFW2:

Inside the filter wheel are AstroDon LRGB E-series Gen2 filters, and AstroDon Ha, SII and OIII 3nm narrow band filters.

 

[jrista]

Thanks, jrista!
I think I still have half a chance to shooting the sky with my 70-200. I think I have to seriously prepare myself this winter when the sky is clear.
As alexthegreek expressed surprise that you don't use a refractor telescope, I am curious why you don't use a reflector scope. Could you elaborate your reasons and insight to these selections?
Thanks
-r

I did use a reflector for a while. I still have the AstroTech 8" Ritchey-Cretien (AT8RC), however I need to sell it. I am not sure if it is just that the scope is too large for my mount, or what, but I have not had much luck using that scope so far. RCs (Ritchey-Cretien Scopes) use two hyperbolic mirrors. As such, they must be PERFECTLY aligned in order to get good results, however collimating an RC is a royal pain in the butt. Additionally, this is one of the "consumer grade" RCs...so they are not built to high tolerance and their collimation does not seem to hold well. So even when I would get it properly collimated, within a couple of days it would slip back out of collimation.

Once I sell it, I am planning on getting a Celestron EdgeHD SCT scope. These are also mirror scopes, although not pure mirrors like an RC (they have an optical corrector plate in the front of the scope). SCTs use spherical mirrors, though, so collimating is extremely easy. The primary mirror in an SCT, unlike an RC, is used to flocus, so it can "float" a little free, resulting in something called mirror flop (the mirror can shift a little during tracking). Thing is, I would MUCH rather deal with mirror flop (and, according to Celestron, if you handle focusing properly, there is no mirror flop with their EdgeHD scopes) than deal with the difficulty in collimating two hyperbolic mirrors.

I am not sure I'll get the SCT, though. One thing that is a problem inherent to all mirror scopes is cooldown. The primary mirror and the entire OTA has to cool. That results in focus shift. The bigger the scope, the more significant the heat mass that has to cool. If I lived in an area of more stable temperatures, I'd probably already have a Celestron EdgeHD...however here in Colorado, we have such huge temperature swings (lately, 82F during the day, 40F at night!!) that trying to cool a large mirror scope is extremely difficult. I think that may the other part of my problem with the RC...it cools throughout the entire night, and cools so much and the focus shifts so much that I can't keep up with it. Not when using 10, 20, 30 minute exposures. The focus will shift so much DURING the exposure that the exposures are just bad, the stars are very bloated and everything, very little detail (sometimes WORSE detail than my shorter 600mm lens!)

So, I may just be sticking with refractors. I can pick up a longer refractor for higher resolution work, but refractors in general (like my 600mm lens, which IS basically a large refracting telescope) are just easier to deal with. They do have a heat mass and do cool, but I find that my 600mm lens settles within 3 hours, and it's rate of cooling is slow enough that I can get longer exposures without too much problem.

 

[jrista]

Look at that stack of washers! . Do you really use the 600 with the 2x teleconverter?

Yeah, the washers were meant to be temporary, however over the long term, they have actually performed perfectly, so I never replaced them with a solid block of metal like I had intended to.

As for the 2x TC. I have, in the past. Even with the 600mm lens and the 2x TC III...the loss in IQ is a bit too much for me, so I don't use it. I actually haven't used my 2x TC III at all for over a year...so I should really sell the darn thing.

 

[lion rock]

jrista,
Thanks for the detailed reply.
I can understand the expansion/contraction due to ambient thermal changes.
I'm interested in looking at the night sky and stars for a long time (since the Star Trek days), but have not really delve into it. I have a neighbour, he was my brother's grad school advisor in California, and he showed me his 8 inch reflector which triggered my interest again. I may, so many wants and so limited resources and time, get a minimal cost 8 inch reflector with a single parabolic mirror. My needs are totally "pro-amateur", so an inexpensive unit would be fine. Hopefully, I don't have to worry about temperature change too much.
Thank you for the insight. You shoot pure fantastic deep sky photos!
-r

 

[jrista]

jrista,
Thanks for the detailed reply.
I can understand the expansion/contraction due to ambient thermal changes.
I'm interested in looking at the night sky and stars for a long time (since the Star Trek days), but have not really delve into it. I have a neighbour, he was my brother's grad school advisor in California, and he showed me his 8 inch reflector which triggered my interest again. I may, so many wants and so limited resources and time, get a minimal cost 8 inch reflector with a single parabolic mirror. My needs are totally "pro-amateur", so an inexpensive unit would be fine. Hopefully, I don't have to worry about temperature change too much.
Thank you for the insight. You shoot pure fantastic deep sky photos!
-r

If you are just starting AP, then the easiest way to start is to get a small refractor. Something like the William Optics Star71, or if you are willing to spend a bit more money for quality, a StellarVue SV80ST. Refractors are small, light weight, and easy. Reflectors are larger, heavier, both of which affect tracking, require collimation, and in the case of newtonians, have much larger moment arms which affects tracking. Trying to learn AP on a larger scope is very difficult. Some people manage it, but I just want you to be aware of what you are stepping into if you pick up an 8" Newt. It won't be easy.

Also remember, you must have a tracking mount if you are going to be imaging at anything much longer than about 50mm. If you are imaging longer than 200mm, a decent german equatorial will be necessary. The lowest end I like to recommend is the Orion Sirius, which is about a grand, and can handle at most a 30lb load. For imaging, you don't really want to load a mount with more than about 50% of that maximum, so 15, maybe 18 pounds. An 8" Newt would require a more sturdy mount, probably something in the $2k range (say the Orion Atlas Pro). A small refractor, however, would be perfect on the Orion Sirius.

 

[lion rock]

jrista,
Thank you again for the pointers. Really appreciate the advice.
This is what I'm lusting after, Meade R8 LX70 8" Reflector on LX70 Equatorial Mount, at a reasonable amateurish cost. It has a low cost drive option, so I think it is adequate for me presently. (Sorry, my GAS fund is for a long white!)
If you think that this model is really below par, I'll look into the ones you suggest.
I thank you for taking time to give me your wisdom.
-r

If you are just starting AP, then the easiest way to start is to get a small refractor. Something like the William Optics Star71, or if you are willing to spend a bit more money for quality, a StellarVue SV80ST. Refractors are small, light weight, and easy. Reflectors are larger, heavier, both of which affect tracking, require collimation, and in the case of newtonians, have much larger moment arms which affects tracking. Trying to learn AP on a larger scope is very difficult. Some people manage it, but I just want you to be aware of what you are stepping into if you pick up an 8" Newt. It won't be easy.

Also remember, you must have a tracking mount if you are going to be imaging at anything much longer than about 50mm. If you are imaging longer than 200mm, a decent german equatorial will be necessary. The lowest end I like to recommend is the Orion Sirius, which is about a grand, and can handle at most a 30lb load. For imaging, you don't really want to load a mount with more than about 50% of that maximum, so 15, maybe 18 pounds. An 8" Newt would require a more sturdy mount, probably something in the $2k range (say the Orion Atlas Pro). A small refractor, however, would be perfect on the Orion Sirius.

 

[telemaq76]

the seven sisters
42x4 min + darks, flats, offsets

 

[Click]

Beautiful picture, telemaq76.

 

[rpt]

the seven sisters
42x4 min + darks, flats, offsets

Lovely picture.

What did you shoot it with? What was the focal distance of the lens?

 

[Mr Bean]

I did use a reflector for a while. I still have the AstroTech 8" Ritchey-Cretien (AT8RC), however I need to sell it. I am not sure if it is just that the scope is too large for my mount, or what, but I have not had much luck using that scope so far. RCs (Ritchey-Cretien Scopes) use two hyperbolic mirrors. As such, they must be PERFECTLY aligned in order to get good results, however collimating an RC is a royal pain in the butt. Additionally, this is one of the "consumer grade" RCs...so they are not built to high tolerance and their collimation does not seem to hold well. So even when I would get it properly collimated, within a couple of days it would slip back out of collimation.

Ah, that bought back memories. 30 years ago, as a hobby, I used to make telescopes (reflectors). I started to make a Ritchey-Cretien but never finished it. I still have the primary (with hole cut) and roughly ground to the shape I needed (done with a diamond edged lens cutting wheel - used on a machine called a "generator"). The good 'ol days

And thanks for the detailed info you provide in your posts jrista.

 

[Mr Bean]

the seven sisters
42x4 min + darks, flats, offsets

Love the image

 

[telemaq76]

the seven sisters
42x4 min + darks, flats, offsets

Lovely picture.

What did you shoot it with? What was the focal distance of the lens?

i used my canon 700da+500mm f4
22x4 minutes + dark, flat offset
new picture of california nebula

 

[Click]

This is a beautiful picture. Well done, telemaq76.

 

[rpt]

i used my canon 700da+500mm f4
22x4 minutes + dark, flat offset
new picture of california nebula

Cool! Thanks. And a lovely picture.

 

[jrista]

jrista,
Thank you again for the pointers. Really appreciate the advice.
This is what I'm lusting after, Meade R8 LX70 8" Reflector on LX70 Equatorial Mount, at a reasonable amateurish cost. It has a low cost drive option, so I think it is adequate for me presently. (Sorry, my GAS fund is for a long white!)
If you think that this model is really below par, I'll look into the ones you suggest.
I thank you for taking time to give me your wisdom.
-r

If you are just starting AP, then the easiest way to start is to get a small refractor. Something like the William Optics Star71, or if you are willing to spend a bit more money for quality, a StellarVue SV80ST. Refractors are small, light weight, and easy. Reflectors are larger, heavier, both of which affect tracking, require collimation, and in the case of newtonians, have much larger moment arms which affects tracking. Trying to learn AP on a larger scope is very difficult. Some people manage it, but I just want you to be aware of what you are stepping into if you pick up an 8" Newt. It won't be easy.

Also remember, you must have a tracking mount if you are going to be imaging at anything much longer than about 50mm. If you are imaging longer than 200mm, a decent german equatorial will be necessary. The lowest end I like to recommend is the Orion Sirius, which is about a grand, and can handle at most a 30lb load. For imaging, you don't really want to load a mount with more than about 50% of that maximum, so 15, maybe 18 pounds. An 8" Newt would require a more sturdy mount, probably something in the $2k range (say the Orion Atlas Pro). A small refractor, however, would be perfect on the Orion Sirius.

The LX70 by default is not a powered mount. There is a drive addon, but it is completely, totally worthless for imaging. Additionally, a scope that large and heavy on a mount that tiny is WAY overloaded. There is not a chance you would be able to use the $700 mount+scope kit to do any imaging.

The bare-bones minimum mount I recommend for use for astrophotography is the Orion Sirius EQ-G. That mount alone is $1100 I think. A decent refracting telescope for imaging purposes comes in around a grand, however the one I like to recommend most often, the SV80ST, is about two grand. So the bare bones imaging kit with a refracting telescope is $3000. IF you want to get into DSO imaging and do it right, and reliably.

You can start more cheaply than that, for sure. Don't even bother with the low end visual kits, like the Mead LX70 ones. I've used similar kits, tried them back in 2013 when I was first getting interested. Totally not worth the hassle. They are visual only. You can pick up a Polari, SkyTracker, or Star Adventurer tracker for about $400-500. Those are very basic trackers, once polar aligned, they can track a DSLR with a lens across the sky, for wide field imaging. You could put up to maybe a 200mm lens on a DSLR on one of those things, and get about 2 hours of good tracking. You can use the camera and lenses you have, for the most part, as well. So they are about the cheapest way to get into astrophotography.

It's not really cheaper than that, though. If you picked up a used Orion Sirius mount, you might spend about $700 or so. If you picked up a used SV80ST, you might spend $900 to $1200. Going used, that is probably the cheapest you can get a decent mount and scope for. You might be able to pick up an AstroTech refractor for cheaper...but they are pretty small, 65mm apertures, fairly slow. I don't like to recommend anything smaller than an 80mm aperture when it's a refractor. I wouldn't think about reflectors yet. They are much larger, heavier, usually longer, and the higher magnification requires things like guiding and more skill with AP to get usable data out of them.

Start out right...with a proper mount, a small 80mm refractor, and adapt your DSLR, and learn the ropes first.

 

[lion rock]

jrista,
Thank you for the advice.
I really have to purpose my funds wisely, and if you think my selection is too simplistic, I'll just shelf it and put my funds into a longer prime as I really AM lusting after. I did hesitate to get the Meade, deep in my heart, I know the product won't be superior with that cost, thus I never made the move. Thanks for setting me straight. I now have to play with my neighbours scope.

I do have the SkyTracker and it ought to pair well with my 70-200 with my 5D3 or 7D2 to give a better "focal length." I'll try my setup when the night sky becomes clearer in the winter months.

In the meantime, I'll have to admire your shots. Hope you'll keep posting them.
Thank you much again for the advice.
-r

 

[jrista]

jrista,
Thank you for the advice.
I really have to purpose my funds wisely, and if you think my selection is too simplistic, I'll just shelf it and put my funds into a longer prime as I really AM lusting after. I did hesitate to get the Meade, deep in my heart, I know the product won't be superior with that cost, thus I never made the move. Thanks for setting me straight. I now have to play with my neighbours scope.

I do have the SkyTracker and it ought to pair well with my 70-200 with my 5D3 or 7D2 to give a better "focal length." I'll try my setup when the night sky becomes clearer in the winter months.

In the meantime, I'll have to admire your shots. Hope you'll keep posting them.
Thank you much again for the advice.
-r

If you have the SkyTracker, then you can actually do a lot with that. At 200mm, you can get some pretty amazing large field nebula shots. Such as framing both Heart and Soul nebulas in a single image. I would definitely give it a try! There are tons of regions in the sky packed with hydrogen gas that will fill a 200mm field quite nicely.

 

[lion rock]

jrista,
Thanks, that gives me a lot of confidence to go with my current lens. I'll shoot some with what I have now.
I'll also try with both my FF and cropped frame and my 1.4X and 2X multiplier. I'm excited.
-r

If you have the SkyTracker, then you can actually do a lot with that. At 200mm, you can get some pretty amazing large field nebula shots. Such as framing both Heart and Soul nebulas in a single image. I would definitely give it a try! There are tons of regions in the sky packed with hydrogen gas that will fill a 200mm field quite nicely.

 

[jrista]

Taurid Meteor through the heart of Pleiades

This new ASI1600 is an incredibly sensitive camera, so it's forced me to use shorter exposures. I was acquiring short 10 second L filter subs two nights ago, and while blinking through them with PixInsight to find and discard bad subs, I noticed something bright flash through one of the frames. When I investigated more closely, I found this amazing sequence:

Meteorite, I believe a Taurid, a minor meteor shower which peaked tonight, zipped through my frames leaving a smoking plasma trail behind, corkscrewing off the right side of the field.