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Old 15-11-2020, 10:52 AM
AdamJL
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Help Choose Next Upgrade

Hi all

Looking for some advice as to my next "upgrade".
I currently use:
Mount: EQ6-R Pro
Scope: Skywatcher ED80 (no field flattener)
Camera: Canon 5D IV not modified
Alignment: PoleMaster
Software: NINA, SynScanPro for alignment (using NINA's inbuilt crosshair)

The issues I'm finding are
- the edge quality of the scope. It's only really useable in the centre
- the inability to shoot emission nebula in more detail with the 5D
- I can get 3+ minutes tracking when facing south, but when I turn east, I seem to only be able to hit 1 minute before trails appear, so a guide-system is necessary in future.

Just after some opinions here. What would you upgrade?
My gut feeling is to go after a new camera. Whether that's a dedicated astro-cam or an EOS Ra (not modding any of my normal cameras) is something I'll decide later, but I feel that if guiding accuracy and edge quality becomes irrelevant if the camera can't actually capture what I want it to capture.
So my thoughts are camera first (which will also crop into the centre of the imaging circle, minimising edge quality issues on the scope), then a field flattener after that.

What do you all think?
Cheers
Adam
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  #2  
Old 15-11-2020, 01:55 PM
AdamJL
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thought I'd share an image from last night. The left hand side really shows how much a field flattener would help
First time I've tried shooting this nebula, and whilst StarTools brings a lot more detail out compared to Photoshop (for me), I'm still not pleased with this.
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  #3  
Old 15-11-2020, 04:18 PM
Xeteth (David)
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First thing I'd be investing in is a field flattener. You'll get much better results with that and your current camera.

From there, the question really becomes what exactly are you trying to achieve? If you want longer exposures then maybe guiding would help, but where are you shooting from? If it's from a light polluted area then longer exposures won't really help you - I'd suggest going narrowband instead.

A dedicated astro camera with cooling really, really helps in reducing noise so that might be the way to go (either color or mono). But yeah, first thing before any other purchase I'd get a field flattener.
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Old 15-11-2020, 05:51 PM
AdamJL
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Thanks David. Currently looking at the Orion flattener, as I believe it doesn't reduce the aperture ratio either, unlike the Sky-Watcher variant which knocks it back 0.85x. I'd prefer to keep the focal length as is.

Quote:
Originally Posted by Xeteth View Post
From there, the question really becomes what exactly are you trying to achieve? If you want longer exposures then maybe guiding would help, but where are you shooting from? If it's from a light polluted area then longer exposures won't really help you - I'd suggest going narrowband instead.

A dedicated astro camera with cooling really, really helps in reducing noise so that might be the way to go (either color or mono). But yeah, first thing before any other purchase I'd get a field flattener.
I do shoot a lot from a Bortle 7 site, and if I go down the path of a filter, then that would likely force me to get something to guide with, right? My understanding is my exposures will drop significantly, if I get something like the Optolong L-Enhance.
That said, I also like to drive out to a Bortle 3 site about 1.5 hours from Sydney, so the filter isn't necessary there. At moment it's about a 60/40 split to shooting in Sydney.

The reason I thought of a camera was because I like shooting emission nebulae (who doesn't) and I am missing a lot of that from the shots I've taken. I know my cameras can be modified, but I'd rather not do that and just get the right tool for the right job. Generally I'm not a fan of using one tool for many tasks.
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Old 15-11-2020, 11:34 PM
Xeteth (David)
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Quote:
Originally Posted by AdamJL View Post
I do shoot a lot from a Bortle 7 site, and if I go down the path of a filter, then that would likely force me to get something to guide with, right? My understanding is my exposures will drop significantly, if I get something like the Optolong L-Enhance.
The filter is going to cut a portion of the unwanted light out of the shot. It will also allow you to take longer subs which then would benefit from guiding certainly.

Quote:
Originally Posted by AdamJL View Post
The reason I thought of a camera was because I like shooting emission nebulae (who doesn't) and I am missing a lot of that from the shots I've taken. I know my cameras can be modified, but I'd rather not do that and just get the right tool for the right job. Generally I'm not a fan of using one tool for many tasks.
I had the same problem when I started out on a DSLR, I decided to get the dedicated astro camera. I guess really the final question is to ask what your budget is and prioritise from there. Here are a few things you could do to upgrade your rig.

1. Autoguiding setup - you could do this for around $500 with basic sort of stuff, or a bit more if you wanted more sensitive equipment, allowing for longer subs and more pinpoint stars.

2. Light pollution filter - this is probably the best way to improve your shots before moving up to a dedicated astro camera if you want to continue to use your current DSLR and give it a try. Here's a great article that will explain it better than I ever could - https://www.astropix.com/html/i_astrop/dslr_ha.html

3. Dedicated Astro camera - either one-shot colour (OSC) or mono depending on what you want to do. OSC are generally cheaper and more beginner friendly and will be able to pick up more of that HA in emission nebulas than your DSLR. Note that you will still run into problems with light pollution with a OSC camera, however this can be mitigated through the use of a LP filter. Mono will allow you to do narrowband imaging (as well as colour), but it is more expensive due to camera cost and needing filters for LRGB and Ha/OIII/SII. It's also more complicated in terms of the process of acquiring and processing subs. However, this is a fantastic method for 'cutting through' light pollution to reveal nebulas (but in results in false-colour images). Either way, I'd suggest a camera will a thermo-electric cooler to help reduce noise levels.
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Old 16-11-2020, 01:19 AM
JA
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Quote:
Originally Posted by AdamJL View Post
Hi all

Looking for some advice as to my next "upgrade".
I currently use:
Mount: EQ6-R Pro
Scope: Skywatcher ED80 (no field flattener)
Camera: Canon 5D IV not modified
Alignment: PoleMaster
Software: NINA, SynScanPro for alignment (using NINA's inbuilt crosshair)

The issues I'm finding are
- the edge quality of the scope. It's only really useable in the centre
Hi Adam,

Depending on which flavour of Skywatcher ED 80mm you are using: "Espirit 80ED", Blackdiamond ED80 / "80 EVOSTAR ED" it may have an image circle that doesn't support full-frame sensors like your Canon 5D. The specs for the Espirit 80ED say that it has a 33mm image circle, well short of the minimum 43.3mm image circle required for full frame. The other 80ED models I mentioned, I checked their specs and they do not specify the image circle size, BUT they do say that they work well with APSc sized sensors and don't mention full-frame, so I suspect they too may also fall short of the 43mm required for full frame. It's not entirely clear in their specs. It's something to consider as a reducer will only make it worse (use even less of the full-frame sensor) and a flattener may well be a moot point if the sensor diagonal isn't filled and you are seeing the extreme edges of the (say 33mm) image field and all the aberrations and light fall off associated with the extremes. It might be OK to have a 33mm or so image circle on an APSc sized sensor (28.3mm diagonal), but not OK on a Full-frame sized sensor (43.3mm diagonal), unless of course you are prepared to crop out heavily as you will see the edge aberrations and see extreme vignetting.

I can't be certain which model ED80 (which?) you have of those listed, but it would pay to know its image circle diameter from specs (or measurement) in consideration of its use with a full-frame camera. I believe that is the central issue you should consider in deciding what you'd like to do next.

Best
JA

Last edited by JA; 16-11-2020 at 01:38 AM.
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  #7  
Old 17-11-2020, 10:38 AM
AdamJL
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Quote:
Originally Posted by Xeteth View Post
It will also allow you to take longer subs which then would benefit from guiding certainly.
I can do about 3-4mins unguided at the moment, depending what I'm shooting (south is easier, east seems to be capped at 30-60 seconds after accurate polar and 3-star aligning)...
I guess if I go the filter route, then that necessitates a guiding solution, so it's really upgrading both at the same time?


thank you for the other comments as well. I don't think I'll go down the mono route. Maybe in 5 or so years! For now, OSC is good enough for me.
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Old 17-11-2020, 10:38 AM
AdamJL
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Quote:
Originally Posted by JA View Post
Hi Adam,

Depending on which flavour of Skywatcher ED 80mm you are using: "Espirit 80ED", Blackdiamond ED80 / "80 EVOSTAR ED" it may have an image circle that doesn't support full-frame sensors like your Canon 5D. The specs for the Espirit 80ED say that it has a 33mm image circle, well short of the minimum 43.3mm image circle required for full frame. The other 80ED models I mentioned, I checked their specs and they do not specify the image circle size, BUT they do say that they work well with APSc sized sensors and don't mention full-frame, so I suspect they too may also fall short of the 43mm required for full frame. It's not entirely clear in their specs. It's something to consider as a reducer will only make it worse (use even less of the full-frame sensor) and a flattener may well be a moot point if the sensor diagonal isn't filled and you are seeing the extreme edges of the (say 33mm) image field and all the aberrations and light fall off associated with the extremes. It might be OK to have a 33mm or so image circle on an APSc sized sensor (28.3mm diagonal), but not OK on a Full-frame sized sensor (43.3mm diagonal), unless of course you are prepared to crop out heavily as you will see the edge aberrations and see extreme vignetting.

I can't be certain which model ED80 (which?) you have of those listed, but it would pay to know its image circle diameter from specs (or measurement) in consideration of its use with a full-frame camera. I believe that is the central issue you should consider in deciding what you'd like to do next.

Best
JA

Hi JA

Good point! I've got the EVOSTAR 80ED. I can't find any specs on the image circle, how do I measure it manually?

Thanks for raising this issue!

Adam
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  #9  
Old 17-11-2020, 10:57 AM
jahnpahwa (JP)
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This may sound like a ridiculous idea, but I'd buy a second hand APS-C canon, and astromod it yourself. Just rip out the filter totally. This will cost you under $200 in total. I think my 550d cost me $130. Then whatever you'd like to do with fitlers... clip in or 2" if your focuser/t-ring/flattener has threads for one? Or a 2" filter drawer added to the mix?
I'm not sure what IR/UV cut you need or want in that scenario. But with money saved you might be able to get one of the new duo-/tri-/quad-band filters which would be pretty awesome.

It will mean that your image FOV will be smaller, and the flattener should have less problem covering the field.

Then get guiding going

Rationale here is that I think you can take a modded dslr quite a long way, but its hard to get far without longer exposures away from the pole. And you get to tinker.
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Old 17-11-2020, 02:34 PM
AdamJL
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Quote:
Originally Posted by jahnpahwa View Post
This may sound like a ridiculous idea, but I'd buy a second hand APS-C canon, and astromod it yourself. Just rip out the filter totally. This will cost you under $200 in total. I think my 550d cost me $130. Then whatever you'd like to do with fitlers... clip in or 2" if your focuser/t-ring/flattener has threads for one? Or a 2" filter drawer added to the mix?
I'm not sure what IR/UV cut you need or want in that scenario. But with money saved you might be able to get one of the new duo-/tri-/quad-band filters which would be pretty awesome.

It will mean that your image FOV will be smaller, and the flattener should have less problem covering the field.

Then get guiding going

Rationale here is that I think you can take a modded dslr quite a long way, but its hard to get far without longer exposures away from the pole. And you get to tinker.
Ha, I've got a couple of spare DSLRs lying about that I could mod, but I'd rather not. Mainly because:

Quote:
And you get to tinker.
I no longer have the time to tinker as I get older with life and other hobbies getting in the way! I prefer a "ready-to-go" solution, or as close to it as possible.

Also:

Quote:
its hard to get far without longer exposures away from the pole
Thank you for confirming my suspicions! I should have researched this, but was wondering why I was getting such shorter exposures without trailing when shooting east. Does this mean if I shoot Andromeda, it'll be worse? Or with it being closer to the north pole, I should get a better chance?
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Old 17-11-2020, 05:35 PM
jahnpahwa (JP)
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Quote:
Originally Posted by AdamJL View Post
Thank you for confirming my suspicions! I should have researched this, but was wondering why I was getting such shorter exposures without trailing when shooting east. Does this mean if I shoot Andromeda, it'll be worse? Or with it being closer to the north pole, I should get a better chance?
Oh, I was just thinking it would be restrictive to be stuck near the pole if you want longer exposures For what its worth, i find my guiding is better when i'm going straight overhead, i suppose because the seeing is better.
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Old 19-11-2020, 12:26 PM
raymo
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The further a target is from either celestial pole the shorter your max sub
length can be, so for example the Large Magellanic Cloud is about 18deg from the Southern Celestial Pole, so you will get nice long subs. The constellation of Orion is as far as you can get from either celestial pole,[like the equator on earth] so you will get the shortest possible max length subs.
Andromeda is about 38deg from the North Celestial Pole, so your max sub length will be slightly better than half way between the min and max possible.
This has nothing to do with magnetic N or S poles on a compass, so shooting
east or west or north or south is irrelevant. It is the target's distance from its
nearest celestial pole that decides max sub length. You can see the celestial poles on any star chart or planisphere.
raymo
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