Level of details in prime focus vs eyepiece images

[Devin-M]

So I was planning to have this Bortle 4 place which is under an hour drive for casual AP (bright and easy targets) and this Bortle 2 for serious stuff. The Bortle 2 is a 3 hour drive, but its a mountainous area with lots of camping sites available, which means I can plan for the entire night.

It’s most convenient if you know of a flat area with few trees.

 

[Devin-M]

By the way, when it comes time to balance your lens/camera on your star tracker, these come in very handy… They’re actually intended for focusing cameras with macro lenses but also work wonders for balancing a camera/lens combo on an equatorial mount.

https://www.bhphotovideo.com/c/prod...Adjustable_Camera_Platforms_6.html?ap=y&smp=y

 

[sophiecentaur]

stopped for water ).

So I was planning to have this Bortle 4 place which is under an hour drive for casual AP (bright and easy targets) and this Bortle 2 for serious stuff. The Bortle 2 is a 3 hour drive, but its a mountainous area

Bortle 4 is fine for practicing the procedures and finding out precisely what you need for a session. It's only when doing this stuff 'for real' that you find out what you are doing wrong. A possible six hours of travel can be frustrating if you have to abort for some trivial reason. So wait until you can arrive, unload, put the kit together reliably (and the reverse) and get useful data at the slightly less-perfect site.
Until you can get all available data on the nearer site, you may not get any visible benefit from the better site. Astrophotography is a long-haul business and many urban astronomers manage to get pretty stunning results.

 

[Devin-M]

I look forward to hearing the results of your unusual approach.

I justified the cost in my mind of tripling my camera rig to capture through all 3 of the narrowband filters simultaneously by saying “well I could buy a brand new Sony A9 II mirrorless camera body alone with no lens for $4.5k, or I could buy 2 used nikon d800 bodies that each have 12 more megapixels than the sony, and 2 used 300mm lenses, and 2 used 2x teleconverters, and 2 new star adventurer star trackers, and 2 new intervalometers and 2 new tripods and 2 new macro rails for slightly less money than the sony body alone, and that will cut any given observation time by 2/3rds, but the sony alone would give no benefit to observation time without vast further financial outlays…”

 

[sophiecentaur]

I justified the cost in my mind of tripling my camera rig

I could see where you were going with it. However, cheaper still would be to do what 'everyone else' does and use just one camera. I think you'd need to consider the different exposure times that are necessary when using narrow band filters and that would probably mean that two of the three cameras may not actually be doing anything useful at times.
You will need to use your arrangement for some while before you can assess just how good your choice was in terms of Bang for Buck. I suspect you may end up using two or three mounts and imaging more than one object. That could be a real plus. I have a chum who does astrophotography and passes the time with his enormous Dobsonian doing visual stuff whilst the other kit is gathering data.

 

[Devin-M]

OTA’s received. They’re in better condition than my original rig…

 

[Devin-M]

 

[Devin-M]

quick test shot with the new optics while I'm waiting for the new equatorial mounts...

"anna's hummingbird" - 1/2500th sec, 6400iso, 600mm, f/9, 100% crop

https://www.speakev.com/attachments/img-4433-gif.150742/

https://www.speakev.com/attachments/img-4434-gif.150739/

 

[Devin-M]

the “goldman narrowband array” is nearly complete… astronomik narrowband hydrogen, sulphur & oxygen 6nm clip-in filters, 300mm lenses, 2x teleconverters, d800 dslrs, star adventurer 2i equatorial mounts, still just waiting on a couple tripods and intervalometers…

 

[PhysicoRaj]

Yikes. Is there an adapter that can fit a monochrome atsronomy camera to DSLR lenses directly? Three of them with your filters in them can probably do this job cheaper?

Edit:
Looks like it exists: (you still need 3 trackers, that's next one to address )

 

[sophiecentaur]

Is there an adapter that can fit a monochrome atsronomy camera to DSLR lenses directly?

A camera lens can obviously be adapted for any image sensor but going too far down that road is of questionable worth. Look around the suppliers; if there's a need for it then there must be something on the market.

A telescope OTA, is little more than a lens, a tube and a focus arrangement. The optical requirements are based on Astrophotography and not on general photography. A camera lens has an (auto) iris and a focussing arrangement (an internal motor perhaps) that is not intended for five minute exposures. Long lenses use telephoto optics which keep them short but involve several more elements. You are paying for stuff you don't need and you are not getting some of the things a regular scope can give you.

However, the quality of many good camera lenses (cheap and on the second hand market) will be a lot better than many entry level scopes.

One needs to ask oneself why nearly all the best astro images tend to be taken with scopes with large apertures and very simple lenses.

 

[PhysicoRaj]

A camera lens can obviously be adapted for any image sensor but going too far down that road is of questionable worth. Look around the suppliers; if there's a need for it then there must be something on the market.

A telescope OTA, is little more than a lens, a tube and a focus arrangement. The optical requirements are based on Astrophotography and not on general photography. A camera lens has an (auto) iris and a focussing arrangement (an internal motor perhaps) that is not intended for five minute exposures. Long lenses use telephoto optics which keep them short but involve several more elements. You are paying for stuff you don't need and you are not getting some of the things a regular scope can give you.

However, the quality of many good camera lenses (cheap and on the second hand market) will be a lot better than many entry level scopes.

One needs to ask oneself why nearly all the best astro images tend to be taken with scopes with large apertures and very simple lenses.

I agree. Was simply trying to think through avoiding having multiple DSLR 'bodies' for simultaneous narrowband exposures.

 

[sophiecentaur]

I agree. Was simply trying to think through avoiding having multiple DSLR 'bodies' for simultaneous narrowband exposures.

Horses for courses again. A DSLR will do loads of things that are not needed of Astro work and the sensor has the colour filters built in. Spending sever hundred quid will get you a very good sensor which you can buy to suit your planned subject and you can COOL it too. All the brains have to be supplied by your computer control but you can expect to be using a laptop out there in any case.

I can see that you are fully committed to a multiple camera solution. That is something you will have to learn about. Three DSLR systems, sharing a mount would need to be driven carefully- they can only be operated in sync because you can't poke around on one camera when another is making its exposure. That builds in a fair amount of necessary down-time; you won't get three times the exposure time.

BTW, have you read anywhere of anyone else who has operated a three camera system successfully? Do you have any links to other similar work or opinions about your system?

 

[Devin-M]

I doubt you can get 3 full-frame 36 megapixel astro-cameras for less than 3 second-hand dslr bodies. The D800’s were $3000 USD brand new but I picked up 2 averaging about $700 each…

“At the time of its release, the Nikon D800 became the Dxomark image sensor leader, replacing the Nikon D4 in the top position.[7]”

https://en.m.wikipedia.org/wiki/Nikon_D800

 

[sophiecentaur]

I doubt you can get 3 full-frame 36 megapixel astro-cameras for less than 3 second-hand dslr bodies. The D800’s were $3000 USD brand new but I picked up 2 averaging about $700 each…

“At the time of its release, the Nikon D800 became the Dxomark image sensor leader, replacing the Nikon D4 in the top position.[7]”

https://en.m.wikipedia.org/wiki/Nikon_D800

Are you comparing like with like here? I have to agree that there will be a premium on top end astro cameras but there will be a huge difference in the specs of the two different types of sensor involved. A high res monochrome astro camera does what it says on the tin whereas a colour DSLR camera is designed with different targets in mind.

People are free to make whatever choices they want, of course but unlike with HiFi equipment, there are many astro experts who can produce reliable numerical data to back up their choices of approach. I'd be inclined to read around a lot before committing to spending a lot on any astrophotography system.

Nevertheless, a standard colour camera can produce some really stunning images. It's all in the post processing.

 

[Devin-M]

I don’t need a laptop, I do everything on my phone from polar alignment (finding the right aim point), to visually locating the target with mobile stellarium, to confirming aim by transferring images from camera to phone and then mobile uploading http://nova.astrometry.net/upload for plate solving.

 

[Devin-M]

In my case one camera works decently enough for my needs, but taking a Hubble palette image would take excessive time, so for me 3 cameras is the solution till I run out of targets and want something even higher quality. The cameras aren’t a complete waste… I could even use them on upgraded OTAs in the future.

 

[Devin-M]

Last night I caught an ISS flyover and did a nightscape animation… (with only 1 camera, still waiting on tripods to use the goldman array)

14mm f/4 6min 100iso full frame sensor
https://www.speakev.com/attachments/img-4506-gif.150765/

14mm f/2.8 2min 400iso full frame sensor
https://www.speakev.com/attachments/img-4509-gif.150766/

On the left side of this animation you can see what light pollution looks like when looking from a bortle 4 back towards a bortle 6. The brightest “star” is the planet Jupiter. Saturn is the second brightest to the right and slightly below Jupiter. The core of the Milky Way is visible on the right. Whiskeytown Lake in California, USA is in the foreground.

 

[Devin-M]

I'm pretty impressed that the currently $675 used Nikon D800 DSLR's from 2012 have better image quality than the currently $3820 used Sony A9 II mirrorless from 2019 for less than 1/5th the price, or a currently $5839 used Canon EOS-1D X Mark III DSLR from 2016 for less than 1/8th the price according to:

https://www.dxomark.com/Cameras/

I seriously doubt you could find a used version of one of the other cameras that's higher on the camera sensor quality list for less than the $675 a used D800 currently costs. The D800 from 2012 currently ranks 23rd in all time sensor quality according to the list... better even than a Phase One IQ 180 Digital Back (medium format) with 80 megapixels from 2011 that costed $42490 new (currently $6619 used), according to the list.

 

[PhysicoRaj]

I can see that you are fully committed to a multiple camera solution.

Not fully committed, but I'll see when I can make that method cheap. The 3 camera setup is a bit bulky for me since my astro stuff is usually during hiking and travel. Especially because of 3 tripods and 3 trackers (!), not the 3 DSLRs themselves. But for now my single DSLR rgb should be more than enough.

In the future I will probably setup multiple narrowband working simultaneously and to get the most of it I'll use the cooled astrocams, but having to have 3 separate mounts still irks me a bit.

BTW, have you read anywhere of anyone else who has operated a three camera system successfully? Do you have any links to other similar work or opinions about your system?

Nope, Devin-M is the only inspiration. The video in post #100 caught me a bit (3 of them can be cheaper), but that's it.

 

[Devin-M]

I’m even more shocked there is no Canon camera on the list with a better image sensor than the Nikon D800 from 2012 (currently going for $675 used) except for the Canon EOS R5 from 2020 which is currently selling used for $3.6k USD… over 5x the price…

https://www.dxomark.com/Cameras/

 

[sophiecentaur]

having to have 3 separate mounts still irks me a bit.

There's no need for three separate mounts. People (with domes) frequently keep two or more scopes on one mount but the various scopes are for different purposes, usually.

 

[Devin-M]

The Star Adventurer 2i (currently $425) actually allows for 2 cameras if you add a separately sold ball head.

See pictograms on the manual cover & page 12 figures 11 & 12…

https://inter-static.skywatcher.com/downloads/StarAdv_manual_150722V2_updateds.pdf

Essentially you’d be using the second camera in place of a counterweight.

 

[Devin-M]

While it’s possible to do it I’d hesitate to implement 2 cameras on the mount, mainly because you’ll have quite a time trying to get the thing balanced with 2 cameras (I had to buy a macro-focusing rail just to get one camera balanced in both the declination axis and right ascension axis), and as I think was previously mentioned you don’t want to be messing around with one camera while the other is shooting if they’re both attached to the same mount & if the mirror flips on one of the cameras it will ruin the picture the other one is taking…

 

[sophiecentaur]

you’ll have quite a time trying to get the thing balanced with 2 cameras

I've not tried it but, for a PF member, I'd have thought you could use the cameras to balance each other, to some extent. It always strikes me that the standard 'weights on a stick' solution is heavier, in total than it need be. The weight of the optics always seems a long way (high up) from the polar axis and requires a lot to balance it. Two OTAs slung low (like the anhedral on some aircraft), on either side of the dovetail base could have their CM right on the polar axis. I guess, if the payload is too wide, you might find it fouls the tripod.

But this is a bit of a digression. I shall have to go out in the garden an try an alternative to the standard system which could possibly be a bit 'legacy' and was invented long before multiple scopes and computer guiding was introduced. There could be a lot of money in it for someone . . . . .

 

[Devin-M]

You could get both cameras perfectly balanced on the right ascension axis with both pointing in the exact same direction, but as soon as one of the two cameras swivels on a ball-head, they will be out of balance because you're essentially changing the distance from the fulcrum of one of the cameras, so it will either have more or less leverage on the right ascension axis (from gravity) than the other camera after you finish pointing it.

 

[Devin-M]

I should add that when you use the fine-tune declination adjuster instead of ball head with a single camera & counterweight, you can get it perfectly balanced on the right ascension axis pointing at, say, the north star, but as soon as you swivel the camera on the declination axis, it will be out of balance for essentially the same reason as in the last post... (unless you use something like a macro focusing rail that I mentioned earlier to finely balance the camera+lens on the declination axis.)

 

[sophiecentaur]

You are right but the errors are second order. Unlike most ‘balance’ systems, what I propose (easy for me with arm waving) remains balanced for all mount directions, once set up, if the scopes point parallel.

but now you will introduce the problem of wind.

 

[sophiecentaur]

I found this. An expensive mount, if I'm not mistaken.
See here.

 

[Devin-M]

At least with the Star Adventurer 2i setup polar aligned and balanced as pictured below, I think they will be significantly out of balance in most cases, even if you have them pointing at the same target. Suppose both cameras are “front heavy” on the mounting points due to the lenses. Suppose you want to aim to a target somewhat to the left of the North Star from the initial position. When you point the camera on the left towards the left, the heavy lens will be further from the fulcrum and the lens on the right will be closer to the fulcrum. The camera on the left will pull downwards with greater force ie out of balance. You can slide the central dovetail to compensate but it will be a huge hassle, and the ball joints can also slowly slip especially with heavy cameras mounted sideways.