Help for a total astro noob please :)

[Pharian (Christopher)]

Hi all,

I'm hoping for some help, I'm just starting out trying to do some astrophotography and I could do with some advice please. There are several areas I'm having trouble with or could use some help.

First, my setup is as follows:

• Celestron 8" SCT OTA (black tube) with f6.3 reducer
• Neq6-pro mount with synscan controller
• Orion ST80 guidescope mounted to top of OTA on Losmandy plate
• Canon 600d DSLR with Shoot intervalometer
• Prostar PS-LPGUIDE-C Guide camera (the first generation one, not the version 2 one)
• I also have a laptop, ascom serial to USB cable, various eyepieces ranging from 40mm plossl to 8.8mm ES 82degree, illuminated cross EP, Laser finder, crappy finder scope.
• Big deep cycle car battery in housing with 12v outputs etc

I only use the scope down the nsw south coast at a holiday house at a very dark site, so I tend to try my best while there then work out what I need to know and work on it back home before going down to try it again. I don't get to use my scope that often so I'm trying to nail down as much as I can before I go down again in a couple of weeks.

I threw the camera on last time I was down and got some blurry shots so will be trying my bahtinov mask next time.

Anyway, my questions are:

Camera Settings

I've tested settings and it's happily taking long shots with the intervalometer. However,

• What ISO would you recommend for this setup shooting deep sky? 800? 1600?
• How long should I take subs? 30s? 2.5min? Longer?

Phd2 guiding and guide cam

I am running a Toupsky driver, but I'm not 100% it's the right one. I got the camera second hand off the iis forums but it came with no drivers so I downloaded one, but it may be for the version 2 camera not the 1st generation one, I can't work out which to use.

When I plug it in (and sometimes have to reinstall toupsky) then it finds the camera. I get a white screen in the Toupsky software when I'm inside in the light, then it goes black if I put the lens cap on so I think the camera works.

However, in phd2 I can't get it to work. I've just got the camera plugged in, I set the driver in the drop down to the Toup driver and hit connect. It seems to connect (button goes green at any rate). Then I try to take some darks but it just times out at 16s (no mount or ascom mount, tried both). I've no idea where the problem is. Any suggestions?

Also, any other suggestions of things I am probably doing wrong?

Thanks in advance everybody, chin chin and clear skies!

[Merlin66 (Ken)]

Practise, practise, practise.....

I'd start with ISO 800 and at least 2-3 min subs - the maximum will be determined by your sky glow/ background.

Sounds like you may have the wrong camera for guiding....
Think about something like the QHY5 or ASI120 - easy to use and all software talks nicely to them.
Onwards and Upwards
[EDIT]
It appears that the ProStar is a pretty capable camera....
https://www.myastroshop.com.au/guides/ps-lp-guider.asp

[poppasmurf (Shane)]

Hi Christopher,

I have been using the same guide camera as yours quite successfully for some time now, I don't use the native capture software at all just PHD2. I have tried both the wdm and the ascom driver with success, but have settled on the ascom driver.
Regarding the camera time out, you can safely adjust the camera time out in PHD2 to 30sec or more if needed, to solve that issue if you believe the camera is operating correctly.
If you are not sure about the drivers, the ones I am using at the moment are stable, I have tried attaching the zip files to this post but they are too large a file size, you can pm me with an email and I will send a copy of mine to you.
I actually downloaded what I believe are the latest drivers fairly recently so you could try downloading from web first if you like.

Shane

[sil (Steve)]

What are your expectations and how do you process? Are you expecting to press the shuuter button and have a jpeg ready to show the world saved to your camera memory card? Do you take dark, bias and flat frames too? do you use them all when processing (if at all?).

As far as I'm concerned there is no limit for ISO I deal with it in other ways (eg lots of subs). Ditto exposure time, starting to think its over rated when I can keep pin point stars and bring out faint structures. If you want "pretty pictures" from your astrophotography it all depends and my opinion is camera settings are not that critical but if you are doing actual science then yes there are probably measurable technical limits. But since no two cameras are identical in performance the various type of noise will vary widely to make it meaningless to say "never go above XXX ISO" or whatever. the answer is "it depends". I appreciate wanting to maximise the time you get to use the gear.

So I suggest, as Ken said, to practice. You dont need a telescope to sort out camera settings, or a dark site. just go outside and take photos of Orion (easy find, doesnt need long exposures), try setting say 5sec and put camera on tripod, now set iso to 400 take a shot, change iso up and take another, keep repeating. Ok the stars are probably blurred but this is PRACTICE, youre not looking for a great photo. Take those photos to your computer (with a good screen, not a laptop outside) and look at them, look to see where finer structures around orion are visible in the photos and where they are not (you didnt change shutter speed did you?) this gives you an idea where the Iso limit for YOUR camera is to gather signal you want. Now look again zoomed out and in on the same shots this time looking at the noise ISO introduces and where it overwhelms signal, you especially want little noise on top of nebulosity as it gets hard to remove without damaging structure detail. So again find an iso limit where the noise you feel is too much and where its workable.

Hopefully those two ISO limits will be the same or close so you can decide for yourself a good starting value. Now set the camera iso to that and go outside and grab say 20 subs, same shutter speed still (i havent said to touch anything other than iso). Now stack 5, 10 and 20 subs with your prefered package, this will show you how the iso noise is suppressed and you might decide there is no visible different between a stack of 10 and 20. Now you have answered yourself how many subs to be taking. compare these stacked ones to your original iso test and it may indicate to you a slight increase in iso will give you more signal for little noise increase that will disappear when stacked.

its an iterative process of testing and refining until you arrive at a set of camera settings that you will stick to for everything except solar/lunar/planetary (do testng process again for those settings). The sky is basically uniform in every direction so your settings will suit you well anywhere you point your camera in the sky. There are very few targets which easily overexpose and camera noise changes with temperature so take a few test shots at the start of your session and make sure you are satisfied your settings are giving you subs of quality you expect, orions core is easy to overexpose which you should avoid, so you need to decide on exposure times for yourself and in some cases take two sets at different exposures to combine in processing so you avoid overexposed parts.

If your subs stack up looking brownish thats light pollution, it may still be there at your dark site so you may want to look into a clipin light polution filter for your camera to block that out.

[Pharian (Christopher)]

Thanks for the advice guys, and particular thanks to Shane for the drivers. I'll let you know how I go. Thanks!

[kens (Ken)]

Sounds like you aren't getting the guide cam/scope to focus. To get my ST80 to focus I need a longish extension tube.

[Pharian (Christopher)]

Hi Kens,

I haven't actually tried it with the st80 yet, planning to do that next weekend. What length of extension tube do you think I'll need? Would be a shame to get there and then need that tube.


Cheers, Chris

[poppasmurf (Shane)]

From memory it is 75mm, will let you know for certain when I get a moment to go down to the obs.

[poppasmurf (Shane)]

Sorry, just went and checked and it is a 50mm extension tube.

[Pharian (Christopher)]

Fantastic! Thanks poppasmurf, much appreciated

[poppasmurf (Shane)]

No problem Chris, keep us informed of your progress mate.

Shane

[Pharian (Christopher)]

Hi Shane, sorry to be a pain, but any chance you could post a link to the 50mm extension please? On bintel or somewhere similar. I'm having trouble finding one anywhere, not sure I'm looking for the right thing. Thanks again, Chris

[poppasmurf (Shane)]

Hi Chris,

No problem mate, here is a link to the orion extension from Bintel.

https://www.bintel.com.au/product/or...ube-1-25-inch/


Shane

[Pharian (Christopher)]

Fantastic, thanks again Shane.

I notice in the description it says that this is for use when not using a diagonal. I assume I can't just use a diagonal for guiding because of the mirror image it will cause?

[Merlin66 (Ken)]

After effective calibration, the guide software can handle any secondary optics like diagonals....

[Pharian (Christopher)]

Oh nice one, I might give it a go without the extension tube then. Thanks again all, Chris