Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

I need a scope recommendation

  • Please log in to reply
33 replies to this topic

#1 Aryeh95

Aryeh95

    Lift Off

  • -----
  • topic starter
  • Posts: 8
  • Joined: 07 Mar 2017

Posted 15 March 2017 - 10:35 PM

Today I got a good Craigslist deal. I got an Orion Atlas EQ-G, an 80mm Guidescope and an Orion Starshoot Guidecam for $650. I already have a Nikon D810 DSLR. So I was wondering what should I get for a scope under 1k. I want to get into dso imaging.

Sent from my Nexus 6P using Tapatalk
  • Rollo likes this

#2 Rollo

Rollo

    Messenger

  • *****
  • Posts: 490
  • Joined: 16 Aug 2006
  • Loc: Alpha Centauri

Posted 15 March 2017 - 10:52 PM

Today I got a good Craigslist deal. I got an Orion Atlas EQ-G, an 80mm Guidescope and an Orion Starshoot Guidecam for $650. I already have a Nikon D810 DSLR. So I was wondering what should I get for a scope under 1k. I want to get into dso imaging.

Sent from my Nexus 6P using Tapatalk

Wow, that is a tough question.  There are so many nice scopes to chose from now.   Under 1k,  Stellarvue sells a really nice 80mm ED refractor for $699.  That scope would give some nice results I would think.   Another scope might be the,  Meade 80mm apo refractor for $999.  That scope has a really nice focuser on it.  There are so many to choose from now, but I really believe a ED refractor might work well.  A lot of guys are using them now with excellent results.



#3 Aryeh95

Aryeh95

    Lift Off

  • -----
  • topic starter
  • Posts: 8
  • Joined: 07 Mar 2017

Posted 15 March 2017 - 10:59 PM

Today I got a good Craigslist deal. I got an Orion Atlas EQ-G, an 80mm Guidescope and an Orion Starshoot Guidecam for $650. I already have a Nikon D810 DSLR. So I was wondering what should I get for a scope under 1k. I want to get into dso imaging.

Sent from my Nexus 6P using Tapatalk

Wow, that is a tough question. There are so many nice scopes to chose from now. Under 1k, Stellarvue sells a really nice 80mm ED refractor for $699. That scope would give some nice results I would think. Another scope might be the, Meade 80mm apo refractor for $999. That scope has a really nice focuser on it. There are so many to choose from now, but I really believe a ED refractor might work well. A lot of guys are using them now with excellent results.
I don't know much about telescopes yet. Would I need a coma corrector or field flattener for that?

Sent from my Nexus 6P using Tapatalk

#4 PirateMike

PirateMike

    Viking 1

  • -----
  • Posts: 928
  • Joined: 27 Sep 2013
  • Loc: A Green Dot On A Blue Sea

Posted 15 March 2017 - 11:08 PM

Refractors usually need a field flattener and reflectors usually need a coma corrector.

 

Read some of the posts on this site, you have a lot to learn if astro-imaging is going to be your thing.



#5 cfosterstars

cfosterstars

    Vostok 1

  • -----
  • Posts: 165
  • Joined: 05 Sep 2014
  • Loc: Austin, Texas

Posted 15 March 2017 - 11:09 PM

I checked and the Nikon D810 has a full frame sized chip so vignetting and field flattness are a big concern. I have a canon 6D and for less than 1K$, the astrotech 65mm quad is a great little scope with a very flat field (triplet plus built in flattener). It is about 650$ and has a 460mm FL. It is great for larger objects and wide field shots. 



#6 PirateMike

PirateMike

    Viking 1

  • -----
  • Posts: 928
  • Joined: 27 Sep 2013
  • Loc: A Green Dot On A Blue Sea

Posted 15 March 2017 - 11:42 PM

I checked and the Nikon D810 has a full frame sized chip so vignetting and field flattness are a big concern. I have a canon 6D and for less than 1K$, the astrotech 65mm quad is a great little scope with a very flat field (triplet plus built in flattener). It is about 650$ and has a 460mm FL. It is great for larger objects and wide field shots. 

I second the AT65EDQ. Built in FF (hence the quad), FPL-53 glass, great scope at a great price. Excellent scope to start in AP but you will use it even after you become an expert.

 

FL is 420mm



#7 Merk

Merk

    Ranger 4

  • -----
  • Posts: 371
  • Joined: 19 May 2014
  • Loc: Cyprus, Nicosia

Posted 15 March 2017 - 11:58 PM

I agree for the 65 mm scope. It is a good match for your camera and a perfect start to learn the hobby
  • bobzeq25 likes this

#8 havasman

havasman

    Fly Me to the Moon

  • ****-
  • Posts: 5071
  • Joined: 04 Aug 2013
  • Loc: Dallas, Texas

Posted 16 March 2017 - 12:07 AM

http://www.astropix.com/bgda/bgda.html

 

A friend does wonderful imaging with that AT65EDQ and it will be easier to get right when starting out.


  • bobzeq25 likes this

#9 Jerry Lodriguss

Jerry Lodriguss

    Vendor

  • *****
  • Vendors
  • Posts: 5298
  • Joined: 19 Jul 2008
  • Loc: Voorhees, NJ

Posted 16 March 2017 - 12:28 AM

I like the AT65EDQ, but you are going to get some significant vignetting with a full frame camera like the D810.

 

You can shoot flats, but remember that flat's will correct for the brightness, but they won't correct for the signal-to-noise ratio loss in the corners.

 

Here's a shot with the AT65EDQ on a full-frame Canon 6D, so you can expect similar results.

 

Note that it might not seem that bad in the example below because of Cloudy Nights bright background, and also note that this image is not stretched that much. When you jack up the contrast for faint deep-sky objects, the vignetting is going to seem a lot worse.

 

The AT65 does a great job on APS-C sized sensors.

 

Jerry

Attached Thumbnails

  • Mark.jpg

Edited by Jerry Lodriguss, 16 March 2017 - 12:32 AM.


#10 Cajundaddy

Cajundaddy

    Mariner 2

  • -----
  • Posts: 263
  • Joined: 27 Dec 2016
  • Loc: Cucamonga CA

Posted 16 March 2017 - 12:48 AM

Maybe a lame question but for those shooting full frame, can't you just gather data, handle your stacking and processing in post, and then do a final crop to trim out all the vignetting so the end result is effectively an APS-C crop image?  Or crop first and then stack for SN ratio?  When I get vignetting with a long tele in nature photography I usually crop it first for composition and to trim the shadows and then process the image.  What am I missing with AP? 



#11 Ranger Tim

Ranger Tim

    Apollo

  • *****
  • Posts: 1142
  • Joined: 25 Mar 2008
  • Loc: SE Idaho, USA

Posted 16 March 2017 - 06:10 PM

Short focal length refractor is the hands-down favorite recommendation from the folks here, with a few others offended that their particular favorite has been ignored. Just sayin'. Yes, you will need a field flattener for most of these to have good success with stars out to the corners of the frame. Some, such as the quadruplet have a built-in flattener. Be sure to figure the extra cost into the comparisons.

 

Me? I use lots of scopes of different types. There is an ancient saying, "House done, man die." I feel the same way about telescopes!



#12 Jerry Lodriguss

Jerry Lodriguss

    Vendor

  • *****
  • Vendors
  • Posts: 5298
  • Joined: 19 Jul 2008
  • Loc: Voorhees, NJ

Posted 16 March 2017 - 06:34 PM

Maybe a lame question but for those shooting full frame, can't you just gather data, handle your stacking and processing in post, and then do a final crop to trim out all the vignetting so the end result is effectively an APS-C crop image?  Or crop first and then stack for SN ratio?  When I get vignetting with a long tele in nature photography I usually crop it first for composition and to trim the shadows and then process the image.  What am I missing with AP? 

Sure, you can crop it.

 

You're spending a LOT of extra money for a Nikon D810, which is what the OP has, and then throwing away all of the extra data in the field of view that a full-format sensor gives you.

 

Which you could have done for $500 with a Nikon D5300 instead of $2,800 for the D810 (which costs more than 5 times a much).

 

But, sure, you can do it.

 

Jerry



#13 Cajundaddy

Cajundaddy

    Mariner 2

  • -----
  • Posts: 263
  • Joined: 27 Dec 2016
  • Loc: Cucamonga CA

Posted 16 March 2017 - 06:55 PM

Ya, I guess that's my point.  If someone was going to buy a camera specifically for AP, it makes sense to match the sensor to your optics.  If he already owns the full frame and wants to use it for AP, a little trimming of shadows is not a crime.  I personally don't like the idea of hanging a $3k Nikon out in the elements off my scope all night.  Bad things can happen in the cold, wet, and dark.  I would probably find a good used APS-C body and have it modified for AP use, or go with a dedicated cooled camera and leave the D810 tucked in my warm closet at home.



#14 bobzeq25

bobzeq25

    Fly Me to the Moon

  • ****-
  • Posts: 7316
  • Joined: 27 Oct 2014

Posted 16 March 2017 - 10:05 PM

I view the vignetting shown by Jerry in #9 as minimal, I wouldn't have any concerns about compensating with flats.  Which is what I'd do rather than crop, as a general rule.  I can see the possibility of specific images being better cropped.



#15 nathang123

nathang123

    Vostok 1

  • -----
  • Posts: 184
  • Joined: 02 Feb 2015

Posted 17 March 2017 - 12:32 AM

 

Maybe a lame question but for those shooting full frame, can't you just gather data, handle your stacking and processing in post, and then do a final crop to trim out all the vignetting so the end result is effectively an APS-C crop image?  Or crop first and then stack for SN ratio?  When I get vignetting with a long tele in nature photography I usually crop it first for composition and to trim the shadows and then process the image.  What am I missing with AP? 

Sure, you can crop it.

 

You're spending a LOT of extra money for a Nikon D810, which is what the OP has, and then throwing away all of the extra data in the field of view that a full-format sensor gives you.

 

Which you could have done for $500 with a Nikon D5300 instead of $2,800 for the D810 (which costs more than 5 times a much).

 

But, sure, you can do it.

 

Jerry

 

This is mostly true. But he's also getting lossless 14 bit NEF files, which you won't get with a D5300. There is certainly some value in that (if not the $2300 delta).

Anyway, to the OP:
I know a lot of people here are big refractor fans (and I do understand the attraction), but if I already had an EQ-G, guider, and a good full frame Nikon and were trying to find a decent, cheap scope to put in front of it, I'd go with an 8" Orion f/3.9 reflector and a Baader MPCC Mk III. With a 4.88 um pixel size and 800mm FL, that's 1.26 arc-sec/pixel...  enough reach for a ton of DSOs, and requiring about 1/3 the exposure length of the AT65EDQ on a given target, even with the significant extra reach. And still a little over 2.5 degrees horizontal FOV without bad vignetting, so you won't have to mosaic anything unless it's just REALLY big (in which case, I would save time and use a camera lens). But, if you hate diffraction spikes, a bit more of a learning curve (but being real, it's still VERY simple), pre-cooling a big mirror, hauling an 8" diameter tube instead of a shorter 2.5" diameter tube, and taking 5 minutes to collimate most times you drive around with it.... best to look elsewhere.
 



#16 Jerry Lodriguss

Jerry Lodriguss

    Vendor

  • *****
  • Vendors
  • Posts: 5298
  • Joined: 19 Jul 2008
  • Loc: Voorhees, NJ

Posted 17 March 2017 - 01:34 AM

 

 

Maybe a lame question but for those shooting full frame, can't you just gather data, handle your stacking and processing in post, and then do a final crop to trim out all the vignetting so the end result is effectively an APS-C crop image?  Or crop first and then stack for SN ratio?  When I get vignetting with a long tele in nature photography I usually crop it first for composition and to trim the shadows and then process the image.  What am I missing with AP? 

Sure, you can crop it.

 

You're spending a LOT of extra money for a Nikon D810, which is what the OP has, and then throwing away all of the extra data in the field of view that a full-format sensor gives you.

 

Which you could have done for $500 with a Nikon D5300 instead of $2,800 for the D810 (which costs more than 5 times a much).

 

But, sure, you can do it.

 

Jerry

 

This is mostly true. But he's also getting lossless 14 bit NEF files, which you won't get with a D5300. There is certainly some value in that (if not the $2300 delta).
 

 

Show me where it makes a difference.

 

Jerry



#17 nathang123

nathang123

    Vostok 1

  • -----
  • Posts: 184
  • Joined: 02 Feb 2015

Posted 17 March 2017 - 02:42 AM

 

 

Show me where it makes a difference.

 

Jerry

 

Ummm... I didn't know that whether a difference exists in the resultant data from lossless and lossy compression algorithms was up for debate. But, since it was requested, I have attached a mask of "a difference". Now don't take this to mean that it's "a difference" that would have to matter to you. It's all just bits. If you don't miss them when they're gone then that's perfectly fine... but in a hobby where people obsess over single electrons in a sensor well, somebody might. I know this is all "pedantry begets pedantry", but I'm forced to point out a real technical difference between the two that does exist and could potentially have negative impacts if you're using the full dynamic range of the sensor, because something has to be thrown out (and I would almost bet that no person has done the requisite work to determine that it does not have a significant deleterious effect on something like near saturation star color, as might be suspected by one familiar with the known function of the algorithm). The resultant data from this sort of compression simply has to be worse, even if it's by an amount that the majority wouldn't notice or would happily trade for meager file size reduction. This is irrefutable. But really, this is not a very worthwhile argument to enter.

Attached Thumbnails

  • lossy.jpg


#18 CodeBlind

CodeBlind

    Explorer 1

  • -----
  • Posts: 72
  • Joined: 02 Feb 2017
  • Loc: New Mexico, USA

Posted 17 March 2017 - 12:22 PM

It's true that lossy vs lossless is going to make a difference, but whether that difference is worth $2300 probably depends more on the optics and techniques being used in the first place. In the music recording industry, there's a saying about this: "It ain't the tool, it's the fool." smile.gif

 

Seems like this is all kind of moot, since the original poster already has a Nikon D810 and now needs a scope.  My recommendation would be a decent refractor.  If I had to do it all over again with $1k-or-less scope budget, I'd get an Explore Scientific 102mm Triplet APO, like this one. The Atlas EQ-G is a solid mount and will handle the weight, and your 80mm guide scope setup will be well-suited to the focal length of the ES102ED.  You will probably get a fair amount of light falloff when using your full-frame DSLR, but I wouldn't worry about that at all until you get a few sessions under your belt anyway.  My first setup was an ES127CF with a Canon EOS 6D, and I've been able to get really nice results, like this one below.

 

Is there light falloff in the corners?  Sure (and it could be a little worse on the ES102ED).  Could this image use improvement?  Absolutely.  Are these issues enough to keep me from enjoying the results produced by shooting like this?  No.

Attached Thumbnails

  • orion-binned.jpg

Edited by CodeBlind, 17 March 2017 - 12:25 PM.

  • Merk likes this

#19 Jerry Lodriguss

Jerry Lodriguss

    Vendor

  • *****
  • Vendors
  • Posts: 5298
  • Joined: 19 Jul 2008
  • Loc: Voorhees, NJ

Posted 17 March 2017 - 12:33 PM

 

 

 

Show me where it makes a difference.

 

Jerry

 

Ummm... I didn't know that whether a difference exists in the resultant data from lossless and lossy compression algorithms was up for debate. But, since it was requested, I have attached a mask of "a difference". Now don't take this to mean that it's "a difference" that would have to matter to you. It's all just bits. If you don't miss them when they're gone then that's perfectly fine... but in a hobby where people obsess over single electrons in a sensor well, somebody might. I know this is all "pedantry begets pedantry", but I'm forced to point out a real technical difference between the two that does exist and could potentially have negative impacts if you're using the full dynamic range of the sensor, because something has to be thrown out (and I would almost bet that no person has done the requisite work to determine that it does not have a significant deleterious effect on something like near saturation star color, as might be suspected by one familiar with the known function of the algorithm). The resultant data from this sort of compression simply has to be worse, even if it's by an amount that the majority wouldn't notice or would happily trade for meager file size reduction. This is irrefutable. But really, this is not a very worthwhile argument to enter.

 

You posted a picture with absolutely no explanation of your methodology or equipment.

 

If the compression is using a lookup table, it might be lossy, but not perceptible, which is the important thing.

 

Jerry



#20 nathang123

nathang123

    Vostok 1

  • -----
  • Posts: 184
  • Joined: 02 Feb 2015

Posted 17 March 2017 - 04:32 PM

It's true that lossy vs lossless is going to make a difference, but whether that difference is worth $2300 probably depends more on the optics and techniques being used in the first place. 

Pretty much! And I'd say it'd basically never be worth any $2300 difference, but that's something entirely up to the individual.

Seems like this is all kind of moot, since the original poster already has a Nikon D810 and now needs a scope.  

Agree with this, too. 

You posted a picture with absolutely no explanation of your methodology or equipment.

 

If the compression is using a lookup table, it might be lossy, but not perceptible, which is the important thing.

 

Jerry

 

I'm confused about where you're going here. Are you saying that what I provided (screenshot from Jeffrey Friedl's blog) isn't enough evidence of "a difference", therefore there is no reason to think that one exists, or are you actually just agreeing with my statement that "It's all just bits. If you don't miss them when they're gone then that's perfectly fine..." in what appears to be an argumentative manner? Lossy compression makes a difference. You apparently don't care about that difference. I'm totally fine with this! I'm also totally fine with people that would like to have as much data intact as they can from each individual frame (even if based on principal alone) and would find the benefits of lossless compression to be valuable. I have no desire at all to dictate or devalue personal preference... only to point out a reality (which was accomplished prior to this back and forth). D810 has lossless compression, D5300 does not.



#21 bmhjr

bmhjr

    Ranger 4

  • -----
  • Posts: 365
  • Joined: 02 Oct 2015
  • Loc: Colorado

Posted 17 March 2017 - 04:41 PM

I think the D810 would vignette considerably on the Orion f/3.9 (at least my friends 6D does), but the D5300 less so. That is loss of bits to consider.

#22 bobzeq25

bobzeq25

    Fly Me to the Moon

  • ****-
  • Posts: 7316
  • Joined: 27 Oct 2014

Posted 17 March 2017 - 04:47 PM

 

 

Maybe a lame question but for those shooting full frame, can't you just gather data, handle your stacking and processing in post, and then do a final crop to trim out all the vignetting so the end result is effectively an APS-C crop image?  Or crop first and then stack for SN ratio?  When I get vignetting with a long tele in nature photography I usually crop it first for composition and to trim the shadows and then process the image.  What am I missing with AP? 

Sure, you can crop it.

 

You're spending a LOT of extra money for a Nikon D810, which is what the OP has, and then throwing away all of the extra data in the field of view that a full-format sensor gives you.

 

Which you could have done for $500 with a Nikon D5300 instead of $2,800 for the D810 (which costs more than 5 times a much).

 

But, sure, you can do it.

 

Jerry

 

This is mostly true. But he's also getting lossless 14 bit NEF files, which you won't get with a D5300. There is certainly some value in that (if not the $2300 delta).

Anyway, to the OP:
I know a lot of people here are big refractor fans (and I do understand the attraction), but if I already had an EQ-G, guider, and a good full frame Nikon and were trying to find a decent, cheap scope to put in front of it, I'd go with an 8" Orion f/3.9 reflector and a Baader MPCC Mk III. With a 4.88 um pixel size and 800mm FL, that's 1.26 arc-sec/pixel...  enough reach for a ton of DSOs, and requiring about 1/3 the exposure length of the AT65EDQ on a given target, even with the significant extra reach. And still a little over 2.5 degrees horizontal FOV without bad vignetting, so you won't have to mosaic anything unless it's just REALLY big (in which case, I would save time and use a camera lens). But, if you hate diffraction spikes, a bit more of a learning curve (but being real, it's still VERY simple), pre-cooling a big mirror, hauling an 8" diameter tube instead of a shorter 2.5" diameter tube, and taking 5 minutes to collimate most times you drive around with it.... best to look elsewhere.
 

 

Lossless makes less of a difference than you think, because...

 

Nikon has a clever algorithm that restricts the compression to the upper bits, an area that is of relatively little value in astrophotography.  Your terrestrial example has little relevance.  I'm sure that wasn't a plan, still, it worked out well.  It's not a case of personal standards, it's a case where the difference is either unnoticeable, or nearly so.

 

The 810 is better because it has a larger FOV.  That's the only really important thing.

 

With an AVX the value of the 8" Newtonian decreases.  With someone trying to "get into" AP, the refractor becomes the obvious, and better, choice.


Edited by bobzeq25, 17 March 2017 - 04:50 PM.


#23 Jerry Lodriguss

Jerry Lodriguss

    Vendor

  • *****
  • Vendors
  • Posts: 5298
  • Joined: 19 Jul 2008
  • Loc: Voorhees, NJ

Posted 17 March 2017 - 05:11 PM

 

It's true that lossy vs lossless is going to make a difference, but whether that difference is worth $2300 probably depends more on the optics and techniques being used in the first place. 

Pretty much! And I'd say it'd basically never be worth any $2300 difference, but that's something entirely up to the individual.

Seems like this is all kind of moot, since the original poster already has a Nikon D810 and now needs a scope.  

Agree with this, too. 

You posted a picture with absolutely no explanation of your methodology or equipment.

 

If the compression is using a lookup table, it might be lossy, but not perceptible, which is the important thing.

 

Jerry

 

I'm confused about where you're going here. Are you saying that what I provided (screenshot from Jeffrey Friedl's blog) isn't enough evidence of "a difference", therefore there is no reason to think that one exists, or are you actually just agreeing with my statement that "It's all just bits. If you don't miss them when they're gone then that's perfectly fine..." in what appears to be an argumentative manner? Lossy compression makes a difference. You apparently don't care about that difference. I'm totally fine with this! I'm also totally fine with people that would like to have as much data intact as they can from each individual frame (even if based on principal alone) and would find the benefits of lossless compression to be valuable. I have no desire at all to dictate or devalue personal preference... only to point out a reality (which was accomplished prior to this back and forth). D810 has lossless compression, D5300 does not.

 

You are way overthinking this. 

 

You presented an image as proof of your argument, but, as I said, you didn't post any explanation as to what it was supposed to be showing, or how it was taken, or what it was taken with.

 

Generally, you might want to provide this information as a courtesy to help inform and educate the people who would want to view the image and actually learn something from it.

 

Otherwise, folks, like me, are just going to shrug and say "I have no idea what this image is, or what it's supposed to show because there is, literally, no information with it".

 

Jerry



#24 17.5Dob

17.5Dob

    Mercury-Atlas

  • *****
  • Posts: 2845
  • Joined: 21 Mar 2013
  • Loc: Colorado,USA

Posted 17 March 2017 - 11:05 PM

 

 

 

Maybe a lame question but for those shooting full frame, can't you just gather data, handle your stacking and processing in post, and then do a final crop to trim out all the vignetting so the end result is effectively an APS-C crop image?  Or crop first and then stack for SN ratio?  When I get vignetting with a long tele in nature photography I usually crop it first for composition and to trim the shadows and then process the image.  What am I missing with AP? 

Sure, you can crop it.

 

You're spending a LOT of extra money for a Nikon D810, which is what the OP has, and then throwing away all of the extra data in the field of view that a full-format sensor gives you.

 

Which you could have done for $500 with a Nikon D5300 instead of $2,800 for the D810 (which costs more than 5 times a much).

 

But, sure, you can do it.

 

Jerry

 

This is mostly true. But he's also getting lossless 14 bit NEF files, which you won't get with a D5300. There is certainly some value in that (if not the $2300 delta).

Anyway, to the OP:
I know a lot of people here are big refractor fans (and I do understand the attraction), but if I already had an EQ-G, guider, and a good full frame Nikon and were trying to find a decent, cheap scope to put in front of it, I'd go with an 8" Orion f/3.9 reflector and a Baader MPCC Mk III. With a 4.88 um pixel size and 800mm FL, that's 1.26 arc-sec/pixel...  enough reach for a ton of DSOs, and requiring about 1/3 the exposure length of the AT65EDQ on a given target, even with the significant extra reach. And still a little over 2.5 degrees horizontal FOV without bad vignetting, so you won't have to mosaic anything unless it's just REALLY big (in which case, I would save time and use a camera lens). But, if you hate diffraction spikes, a bit more of a learning curve (but being real, it's still VERY simple), pre-cooling a big mirror, hauling an 8" diameter tube instead of a shorter 2.5" diameter tube, and taking 5 minutes to collimate most times you drive around with it.... best to look elsewhere.
 

 

Lossless makes less of a difference than you think, because...

 

Nikon has a clever algorithm that restricts the compression to the upper bits, an area that is of relatively little value in astrophotography.  Your terrestrial example has little relevance.  I'm sure that wasn't a plan, still, it worked out well.

 

Ding ! Ding ! Ding !

Notice that the shadows in the "example" are totally skipped ! Shooting total darkness, with a - 2-3 Ev under exposure to keep the histo as far left as is possible, makes this a moot point.

But snce the OP already owns the Nikon 810 and IS NOT looking for a new camera, this old thread should come in handy  if the OP hasn't tried a search for FF compatible OTAs.



#25 nathang123

nathang123

    Vostok 1

  • -----
  • Posts: 184
  • Joined: 02 Feb 2015

Posted 18 March 2017 - 12:29 AM

?
I have to say, I would not have expected and have never really seen this level of push back from simply stating (and not backing down from) a fact here. Where my italics not sufficient to downplay the magnitude of the difference and that prompted an emotional response? Jeez.

Lossless makes less of a difference than you think, because...
I'm confused about how you've determined the amount of difference that I think it makes. Something doesn't have to matter greatly to me for it to be pointed out as a real difference that somebody might care about.

 

Nikon has a clever algorithm that restricts the compression to the upper bits, an area that is of relatively little value in astrophotography.  Your terrestrial example has little relevance.  I'm sure that wasn't a plan, still, it worked out well.  It's not a case of personal standards, it's a case where the difference is either unnoticeable, or nearly so.

I'm aware of the behavior. And IMO "nearly so" couldn't be more indicative of a case of "personal standards", but regardless, I have yet to see a single person compare a sufficient amount of astrophotography data (lossy vs. lossless) in a manner that would allow anyone to conclude much of anything beyond supposition. It seems that everyone with a D3___ or D5___ just says "I don't notice any problem, and I can't change it anyway" and goes on with their lives, and people with the option to do either just keep all their bits and go on with their lives. Yes, evidence points to it not doing much away from the areas near saturation. No, that doesn't mean that nobody cares about it.
 

The 810 is better because it has a larger FOV.  That's the only really important thing.
Yes, to you and others, clearly. Believe me, I caught that after being hit over the head with it a few times.

 

With an AVX the value of the 8" Newtonian decreases.  With someone trying to "get into" AP, the refractor becomes the obvious, and better, choice.

What AVX? An EQ-G with a guider can more than adequately keep a little 8" reflector on target, making it a matter of weighing personal pros and cons, NOT an obvious anything. There is nothing wrong with either choice.

 

I think the D810 would vignette considerably on the Orion f/3.9 (at least my friends 6D does), but the D5300 less so. That is loss of bits to consider.
It does vignette, absolutely. I seem to recall near 1 EV on any side and more in extreme corners, nothing outside of normal semi-fast lens falloff (and definitely nothing as hard and relatively uncorrectable as the corners on the refractor pics above), but I don't have the data handy to confirm. I would not consider that level to be of concern on an f/3.9 system. It would be more so on an f/6.3 system where the photons are quite a bit more lacking. 

 

You are way overthinking this. 

People have an astounding insight into my thoughts, it seems.
 

You presented an image as proof of your argument, but, as I said, you didn't post any explanation as to what it was supposed to be showing, or how it was taken, or what it was taken with.

 I thought that difference masks would be generally well enough understood, and I didn't bother expounding. But it's all on his blog, which Bob up there has apparently read or seen referenced at some point, since he partially summarized some of the points made. 
 

Generally, you might want to provide this information as a courtesy to help inform and educate the people who would want to view the image and actually learn something from it.

Fair enough. I can link it later on my normal computer if anyone has trouble finding it. 
 

Otherwise, folks, like me, are just going to shrug and say "I have no idea what this image is, or what it's supposed to show because there is, literally, no information with it".

I was being serious when I said that I thought it would be well enough understood, and sorry if it wasn't. It's supposed to show a difference, which was the only point. If there were no differences, it would be black. There's nothing quantitative about it.
 

Jerry

 




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.







Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics