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Astrophotography Beginner Equipment
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#1 UP4014Fan

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Posted 22 September 2021 - 08:58 PM

Before I start, I will apologize for posting something that has likely been asked a thousand times before.  I have done research here and elsewhere, but I am getting conflicting advice/information.

As background, I've been a serious amateur photographer for 50 years.  Last summer, during the lockdown, I finally started learning how to do astrophotography.  Although I'm still very much a beginner, I believe that I've been a fairly quick study in learning about automated photo sessions, image stacking, signal-to-noise ratios in digital photography (shades of reciprocity failures during my analog days!), the use of Photoshop to bring out the best in the resulting images, and so on.  At this point, I think I've pushed a Canon DSLR, Sigma 120-400 lens (my airshow lens), and Sky Watcher mount about as far as they can go.  BTW, if anyone wants to learn some tricks to bore sighting a hot-shoe mounted iPhone as a spotting scope, let me know.

All that said, I'm in a position to purchase a decent telescope, something I've wanted since I was a kid.  I've been considering the Celestron VX8 as what appears to be the best intersection of my price range vs. performance.  Of course, I know that I'd have to get a focus motor, the appropriate adapter for my Canon bodies, and power supply adapter as well.  However, in reading various articles and the books I've purchased, there are many that seem to think that a Newtonian reflector would be the better choice, or perhaps even a refractor.  One thing that surprised me today was a comment someone made about "mirror flop" with a Schmidt-Cassegrain telescope - unless they're referring to the camera body, I'm at a total loss on that one.

With that said I'm seeking more experienced folks' advice.  A couple of items:

 

1)  I'm not afraid of a somewhat narrow field.  I've learned infinite patience aiming a racked-out 400mm zoom lens at, say, the Pinwheel Galaxy, and taking dozens of ISO 25,600 images as I try to center it.  A computerized mount will be a luxury, to say the least.

 

2)  As you may have inferred from the above, I'm looking to go for deeper space objects as a personal and artistic challenge.  I was happy with the image I got of the Pinwheel, for example, but it was clearly a small object in a wide field using the Sigma.

3) I know the VX8 is relatively slow at f/10.  That doesn't bother me too much as long as the trade off is superior image quality and less work on collimating the telescope (that said, would it be?).

 

4)  Regardless of the optics, I don't want to buy every accessory in the Celestron (or other manufacturer's) catalog.  What, other than the power supply, autofocus motor, and camera adapter, are the essentials and the nice-to-haves I should be considering along with the telescope?

 

Thank you in advance for your patience and advice.

 

 



#2 Oyaji

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Posted 22 September 2021 - 09:33 PM

No. 1 suggestion:  Buy and read this book before doing anything else.  https://digitalstars...s.com/primer/  



#3 madmandrews

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Posted 22 September 2021 - 09:36 PM

The primary mirror in a SCT moves in order to achieve focus - there's a bit of "slop" in the system. When the scope crosses the meridian (possibly involving a meridian flip), there is the potential for movement - the flop - which can throw focus off. I also used a DSLR for years - switched to a dedicated astro camera and never looked back.


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#4 UP4014Fan

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Posted 22 September 2021 - 09:55 PM

The primary mirror in a SCT moves in order to achieve focus - there's a bit of "slop" in the system. When the scope crosses the meridian (possibly involving a meridian flip), there is the potential for movement - the flop - which can throw focus off. I also used a DSLR for years - switched to a dedicated astro camera and never looked back.

Ah!  Thanks - that makes sense now.

As for changing camera bodies - one step at a time.smile.gif


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#5 UP4014Fan

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Posted 22 September 2021 - 09:57 PM

No. 1 suggestion:  Buy and read this book before doing anything else.  https://digitalstars...s.com/primer/  

Thanks - it's already in my library.  I appreciate your validating my purchase of it!



#6 jonnybravo0311

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Posted 22 September 2021 - 09:58 PM

If you're serious about wanting to continue with the hobby of astrophotography, the MOUNT, not the scope should be your first major purchase. Everyone wants new glass. The problem is you can have the best glass in the world, but it won't mean a thing if you don't have a solid mount. You'll produce far better images with a fantastic mount and mediocre glass.

 

The combination you're considering might work well for visual or planetary. It will struggle with long exposure deep sky stuff, especially so if you're considering running it unguided.

 

That, of course, is just my 2 photons of advice. Do with it what you will :)


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#7 Arcamigo

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Posted 22 September 2021 - 10:06 PM

So I was in a similar situation as you, photography for 50 years, always wanted a telescope, etc. There are so many ways to answer your question, so I'll just quickly share what I've learned:

1. It's ok to start with narrow field, but you might be happier starting wide field because it will be easier to keep the stars rounder with less guiding effort - even unguided.

2. Reflector or refractor? Either one will get you great DSO images, but you're going to appreciate a fast telescope for DSO's just like you would appreciate a fast lens on your camera.

3. Just like the tripod is the most important accessory in photography, so is the mount in astrophotography. Get the best mount you can. I started with the Orion EQ-G, but because I don't like using an additional guiding camera, I could only do 60 to 90 sec exposures with a 1000mm, f/5.3 telescope. The periodic error was really messing up my images. I now use an iOptron CEM70EC and, wow, 3 to 10 minutes unguided exposures and no periodic error that I can see.

4. I too started with a DSLR because that's what I knew. I was never happy with my images though, because the filter in front of the sensor was significantly attenuating one of the most important wavelengths in astrophotography. I now use a ZWO ASI2600MC camera controlled by an ASIAIR PRO. The first thing I noticed in my images was all the red I wasn't getting from my DSLR.

Hope this helps.



#8 UP4014Fan

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Posted 22 September 2021 - 10:06 PM

If you're serious about wanting to continue with the hobby of astrophotography, the MOUNT, not the scope should be your first major purchase. Everyone wants new glass. The problem is you can have the best glass in the world, but it won't mean a thing if you don't have a solid mount. You'll produce far better images with a fantastic mount and mediocre glass.

 

The combination you're considering might work well for visual or planetary. It will struggle with long exposure deep sky stuff, especially so if you're considering running it unguided.

 

That, of course, is just my 2 photons of advice. Do with it what you will smile.gif

As you can imagine, I've already had some "fun" with using a high-end tripod, the Sky Watcher, and the Sigma.  I swear if you even look at the aforementioned tracker, it vibrates (seriously, I've found it takes about six seconds after the mirror is locked up for everything to stabilize). 

I have considered the mount as well as the glass and I thought the Celestron equatorial mount and tripod would be reasonably steady.  I'm open to suggestions.  As with lift over drag curves in aviation, there is a sweet spot where the performance of the mount and what my finances can handle intersect.



#9 UP4014Fan

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Posted 22 September 2021 - 10:14 PM

So I was in a similar situation as you, photography for 50 years, always wanted a telescope, etc. There are so many ways to answer your question, so I'll just quickly share what I've learned:

1. It's ok to start with narrow field, but you might be happier starting wide field because it will be easier to keep the stars rounder with less guiding effort - even unguided.

2. Reflector or refractor? Either one will get you great DSO images, but you're going to appreciate a fast telescope for DSO's just like you would appreciate a fast lens on your camera.

3. Just like the tripod is the most important accessory in photography, so is the mount in astrophotography. Get the best mount you can. I started with the Orion EQ-G, but because I don't like using an additional guiding camera, I could only do 60 to 90 sec exposures with a 1000mm, f/5.3 telescope. The periodic error was really messing up my images. I now use an iOptron CEM70EC and, wow, 3 to 10 minutes unguided exposures and no periodic error that I can see.

4. I too started with a DSLR because that's what I knew. I was never happy with my images though, because the filter in front of the sensor was significantly attenuating one of the most important wavelengths in astrophotography. I now use a ZWO ASI2600MC camera controlled by an ASIAIR PRO. The first thing I noticed in my images was all the red I wasn't getting from my DSLR.

Hope this helps.

It does and I appreciate it.  I'll take a look at those mounts

I'm aware of the filter in the standard DSLR.  Since both bodies are my general use cameras, I'm not about to modify them, as I've seen some do.  At some point I will consider a dedicated camera, but one purchase at a time.

As I said in my original post, I could live with a slower lens as a trade for image quality.  That said, if I go with a refractor, any suggestions as to focal length?  The Sigma at 400mm is a pretty wide field, so I'm using that as my baseline.

Thanks again.



#10 jonnybravo0311

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Posted 22 September 2021 - 10:20 PM

As you can imagine, I've already had some "fun" with using a high-end tripod, the Sky Watcher, and the Sigma.  I swear if you even look at the aforementioned tracker, it vibrates (seriously, I've found it takes about six seconds after the mirror is locked up for everything to stabilize). 

I have considered the mount as well as the glass and I thought the Celestron equatorial mount and tripod would be reasonably steady.  I'm open to suggestions.  As with lift over drag curves in aviation, there is a sweet spot where the performance of the mount and what my finances can handle intersect.

I started with a Lumix G9, a 50-200mm lens and a tripod. I added a Star Adventurer shortly thereafter. So, I have also had the "fun". Since I purchased the CEM40, the SA has been sitting in its box. I tell myself I'm keeping it for a "portable travel rig". I haven't made it past the end of my driveway in a year :p. To be honest, unless I was going hiking in some remote location (extremely unlikely to happen) and needed to pack everything into a backpack, I'm far more likely to put the CEM40 in the truck and use that.

 

I don't know where that intersection of performance and finance is for you. What I do know is that even though the AVX is a vast improvement over the SA, paired with an 8" SCT running natively at f/10, you're going to continue to experience the "fun". Except now, it'll be vibrating when your neighbor down the street just looks in your general direction :p.



#11 Arcamigo

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Posted 22 September 2021 - 10:46 PM

It does and I appreciate it.  I'll take a look at those mounts

I'm aware of the filter in the standard DSLR.  Since both bodies are my general use cameras, I'm not about to modify them, as I've seen some do.  At some point I will consider a dedicated camera, but one purchase at a time.

As I said in my original post, I could live with a slower lens as a trade for image quality.  That said, if I go with a refractor, any suggestions as to focal length?  The Sigma at 400mm is a pretty wide field, so I'm using that as my baseline.

Thanks again.

The focal length choice is really entirely up to you depending on what you want to shoot. I'm pretty comfortable with my AT130EDT's 1000mm, or 730mm with the field flattener, but even that is really tight on objects like the Pleiades, North American Nebula, Sadr Region, and more.

 

Stellarium might be helpful here. You can setup your camera and the telescopes you're interested in, and then move around to a few DSOs to see how the images you want would appear. I found that helpful in selecting my most recent telescope with a focal length of 345 mm.

 

You're also going to want a Bahtinov mask for whatever you decide on.



#12 mayhem13

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Posted 22 September 2021 - 10:48 PM

The VX8 is a nice setup for observing, but the mount isn’t accurate enough at the long focal lengths of the 8” SCT it’s paired with for imaging IMO. You can reduce the native focal length of 2032 down to 1200 with the matched .63 reducer, but even that’s a stretch for the AVX and guiding.

 

You seem pretty set on the small deepsky stuff…..so an 8” SCT is the right scope with a reducer allowing for two focal lengths….AND…if you wanna have some fun with planetary, this setup paired with a Barlow lens yields incredible images……lots of options here. You’re just gonna need a better mount……EQ6R Pro, CGX, along those lines. The C8 with a .63 reducer isn’t too slow at F6.3

 

Look on the classifieds here for the optical tube……they pop up used all the time. The mount….well…..I’d get that new. If a user sells a mount, it’s often because it has backlash or other issues that they can’t resolve. 

Now…..the elephant in the room…..the DSLR. So it’s important to limit your targets not only by size but type as well……an un modified DSLR is best suited to broadband imaging, primarily star stuff….galaxies, clusters. Later, when you’re gonna upgrade to a dedicated Astrocam, you can set your sights on Nebulae.

 

8” imaging newts are great…….but they catch the breeze so the same as above applies….heavy duty mount…..and they require a Coma corrector……$$ to donuts the price equals out to that of an 8” SCT. They are fast though at f4 or about…….shorter exposure time equals more tolerant of tracking errors. The focal length is also 800mm which is more tolerant of tracking/guiding error.



#13 Oyaji

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Posted 22 September 2021 - 10:53 PM

UP4014:  I think Johnny Bravo is trying to tell you in a nice way that your C8/AVX will likely disappoint. I didn't want to be the one to break the news to you; I knew somebody else would step up to the plate, so instead, I directed your attention to the Bracken book. And I trust it will become clear from Bracken that while your photography background is useful, you truly have entered a different realm where, for example, NOBODY shoots at 25,600 ISO, and for good reason. 

 

There's a guy, "Uncle Rod", well known in the online astro community, who lays it on the line about imaging with a C8.  https://uncle-rods.b...es-with-c8.html

 

Bottom line, if you want to image with a C8, you are going to need a more capable mount than an AVX.  But also:  seriously consider learning the  astrophotography ropes with a shorter focal length refractor.  You have enough to learn without struggling with the C8. And a shorter f/l refractor might play better with your AVX.

 

And if you "graduate" later to a long focal length scope, you may find that the C8 isn't the best choice for you.  You may want something bigger, smaller, or with better corrected optics or indeed, with no dew-magnet corrector plate.  Trust me; after a year of experience, you will be much better able to make the decision.  

 

P.S.  More by Uncle Rod on mount choices:  https://uncle-rods.b...raphy-with.html


Edited by Oyaji, 22 September 2021 - 11:22 PM.


#14 imtl

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Posted 23 September 2021 - 12:05 AM

This is really not going to go to any specifics unless you say what is your budget. 



#15 Simon B

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Posted 23 September 2021 - 12:52 AM

I think some may try to steer you clear of an SCT, but since you already have experience doing long exposures with a telephoto lens, I say go for it : )  A refractor with a similar focal length will be very heavy, not to mention expensive.

 

The problem with your proposed setup is more the mount - I've never used an AVX but like others have commented, I'm almost certain it won't be adequate for an 8" SCT

I would opt for at least a CGEM II or Skywatcher EQ6R

 

 

You say that it's 'relatively slow at F10' - Celestron have a dedicated reducer that brings it down to F6.3 (1280mm focal length) specifically for astrophotography so you'll almost definitely want that. 1280mm focal length is plenty, and will keep you busy for a very long time

 

 

Best of luck!



#16 idclimber

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Posted 23 September 2021 - 04:08 AM

I am also an long time terrestrial photographer going back to the early days of roll film and medium format cameras as well as F mount Nikkor lenses. 

 

I started with 12" SCT a few years ago, and I also have a 102mm refractor. I would strongly advise against a 8" SCT as well as any of the larger scopes regardless of your budget. The simple fact is that any focal length above about 1000mm is mostly wasted if you have average seeing conditions. 90% of the time I image with the smaller refractor even though I have a mount capable of either. 

 

I do not recommend any of the Celestron mounts. Good for visual, but simply do not meet the quality of either Skywatcher or ioptron for AP. Buy the best mount you can afford especially if you want to image at 2000mm with an 8" SCT.

 

The best size scope to both learn on and capture a ton of targets is about 80mm. I would consider that about the sweet spot. Alternatively you would do well at 60mm as well as up to about 100. The larger the scope and the longer the focal length the more you will be asking from your mount and the more expensive things get. 

 

The more experienced imagers posting in this thread are doing guided imaging and have their mounts tracking below one arc second of measurement for exposures that range from about a minute to about 10. An arc second (abbreviated as ") is a slice of sky about the size of a dime at 2.5 miles away and is a common unit of measure used to quantify the image scale of our imaging systems. On my 102mm refractor that scale is about 1.5" for each pixel. On my 12" SCT that drops to about 0.3" per pixel.

 

There are websites and online calculators that will tell you the suitability of various equipment combinations. I would suggest the CCD suitability over at  http://astronomy.tools


Edited by idclimber, 23 September 2021 - 04:10 AM.

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