First Dive into Imaging (in progress) !

[jpoulette]

Warning - newbie alert  !

So, I've been an alt-az / refractor sky gazer forever - but my New Year's resolution for 2023 was to finally give imaging a try.

The "easy stuff" is going well: Here is the set-up so far, based around the Askar FR400 (for which there is lots of information on this site). It is practically based on Lee's thread here for which I am great full.

Progress so far:

- Build set-up as shown. (highly recommend the PRI-PLLLOS240P PrimaLuceLab 240mm Plate which leaves plenty of room for everything)

- Connect and familiarize myself with ASIair through a PC using Bluestacks X, and through Android. (Test and align focuser, test heaters - not much else until mount arrives)

- Settled on the AM5 for a mount (ordered - will be here next week).

- Complete some rudimentary calculations on the power requirements - decisions to use this power supply with a splitter to de-rate the system enough so I won't worry about it (I work with overly stressed power systems all the time and it literally drives me crazy).

Questions:

- I'd like to ultimately experiment with this 2" 2X Powermate on the main camera (with a 2X Barlow on the guider) , and I'm wondering if it could simply take the place of the adapters supplied with the FRA400 (and refocus of course).

- Best placement of filters (such as the Optolong Dual-Band L-eXtreme 2" Filter).

- I'm sure I'll have a jillion other questions when the mount arrives. 😎Looking forward to posting my first image (hopefully M81) - but I'm going to take it slow and methodical.

Jim

[AstroMuni]

Welcome to the AP club, Jim. Have you decided on a software for the post processing of the images?

[jpoulette]

11 minutes ago, AstroMuni said:

Welcome to the AP club, Jim. Have you decided on a software for the post processing of the images?

Good question. 😀 Any suggestions - please, be my guest !!

Coming from an engineering background - I'm pretty comfortable with most software products I've come across, so I've looked at several. I suspect I'll start with something like Astro Pixel Processor, while at the same time plowing through the rudiments of PixInsight.

PixInsight appears to have the best long-term bang for the buck, but might demand a longer learning curve to master all the bells and whistles. And there appears to be no lack of those.....

Additionally, I need to understand the limitations of this hardware (Stellarium "image sensor frame" mode and error tracking software may help) and get the basics down on frames and exposures also, how many frames, what type of frames, etc. and then go on to post processing from there. There's no rush - so I plan to meander my way through it picking up as much as I can along the way. Luckily there is a LOT of information right here if one looks closely enough.

Jim

[AstroMuni]

9 minutes ago, jpoulette said:

Coming from an engineering background - I'm pretty comfortable with most software products I've come across, so I've looked at several. I suspect I'll start with something like Astro Pixel Processor, while at the same time plowing through the rudiments of PixInsight.

Also look at DSS, Siril (free), Affinity Photo, Photoshop, Startools. Personally I use Siril.

I found it easier to capture the images, but the post processing is the difficult bit. Using my data the experts can get much better images 😞

Edited January 27, 2023 by AstroMuni

[jpoulette]

Very good - thank you !

My wife is a graphic designer - so Photoshop has been around the house here for literally decades. 😀 It may be of use but like I said - we'll take it as it comes for now.

I agree though that acquiring the images is one thing, but getting the most out of them with processing is entirely different !

Jim

[michael8554]

A few observations.

Adding a 2X PowerMate will double the focal length - good for those smaller targets.

But will double the f/ ratio to f/11.2, which will require much longer exposures.

You might be better off just cropping the f/5.7 images.

Why are you putting a 2X Barlow on the guidescope ?

Michael

 

 

[DSviewer]

Nice setup looking at the Askar or William Optics ariound 500-700 focal length

[jpoulette]

1 hour ago, michael8554 said:

A few observations.

Adding a 2X PowerMate will double the focal length - good for those smaller targets.

But will double the f/ ratio to f/11.2, which will require much longer exposures.

You might be better off just cropping the f/5.7 images.

Why are you putting a 2X Barlow on the guidescope ?

Michael

 

 

Frankly, I just like to experiment - I have a good collection of TV Barlows & Powermates so I thought I'd give them a try (at some point). Surely, lots to learn before messing around with that.

I've also been reading a bit about "pixel scaling" in guiding, and though it might be interesting to see this phenomena in actual practice.

I definitely understand the f-ratio and exposure time relationship (2x Barlow ~ 4x exposure time). I also have the Askar reducer (0.7x, f/3.9) and will probably start with that as well. I'll lose FL but as you suggest it will decrease exposure time quite a bit.

With or without the reducer, cropping images will definitely be a good starting point. 😀

Jim

[jpoulette]

OK, so the AM5 and pier are here, set-up and it seems to be working fine. (articulation free of cabling interference snags, but have yet to attempt alignment or focus verification for either scope)

My Bahtinov mask and 'flat hoop' are ready to go, as I continue to familiarize myself with the ASIair application.

So, on my journey to understand frame types and purposes - 2 immediate questions:

1. Do all frames (light, dark, flat, & bias) need to be acquired at the same temperature? (think +65F indoors and +10F outside) a 55F swing just seems like a lot to me.

2. You can reiterate the polar 'alignment' until the cows come home, but what would be a preferred error? Some of the videos suggest < 5' on az/alt, which again seems like a lot.

Thank you in advance ! 

Jim

[iantaylor2uk]

I would use it in equatorial mode rather than alt/az if you plan on taking photos. If the polar alignment is less than 5' then guiding is usually OK. 5' is one twelfth of a degree, so it is pretty close to the pole. You can try to get it closer if you want. I find it easiest to take dark, flat, and bias frames at the telescope under the same conditions as the light frames. For the dark and bias frames just cover the telescope with the lens cover. The dark frames will need to be the same exposure length, gain and temperature as the light frames. I tend to use bias frames rather than bother with dark flats. 

[Lee_P]

It's great to see you're having a good time already reproducing my Askar FRA400 setup  

On 27/01/2023 at 14:17, jpoulette said:

- I'd like to ultimately experiment with this 2" 2X Powermate on the main camera (with a 2X Barlow on the guider) , and I'm wondering if it could simply take the place of the adapters supplied with the FRA400 (and refocus of course).

I think you'll be making things hard for yourself by adding something like that Powermate into your system. The Askar FRA400 is a beast at widefield, so let it shine there  As has been suggested, you can always crop in a fair amount if needed. Having said all that, if you want to try it for a fun experiment then sure, go for it -- but I expect that will be a brief dalliance.

On 27/01/2023 at 14:17, jpoulette said:

- Best placement of filters (such as the Optolong Dual-Band L-eXtreme 2" Filter).

I recommend a ZWO 2″ Filter Drawer with M48 / M42 connections. (This one, but maybe you want to find a supplier local to you).

 

5 hours ago, jpoulette said:

My Bahtinov mask and 'flat hoop' are ready to go, as I continue to familiarize myself with the ASIair application.

I recommend getting a ZWO EAF. Much better than a Bhatinov mask, integrates really well with the ASIAIR, and will fit your Askar FRA400 no problem. EDIT: just seen in your photos that you've got an EAF installed already. Not sure why you're using a Bhatinov mask..?

5 hours ago, jpoulette said:

1. Do all frames (light, dark, flat, & bias) need to be acquired at the same temperature? (think +65F indoors and +10F outside) a 55F swing just seems like a lot to me.

Yes, same temperature for everything. I always set my 2600MC-PRO to run at -10 deg C. Use the same temperature for your light frames too. If you do this then you can build a library of dark and bias frames that you re-use every time.

5 hours ago, jpoulette said:

2. You can reiterate the polar 'alignment' until the cows come home, but what would be a preferred error? Some of the videos suggest < 5' on az/alt, which again seems like a lot.

You'll want equatorial mode, as Ian says. Tweak your polar alignment until the ASIAIR gives you a smiley face. Simple!

Edited January 31, 2023 by Lee_P

[rickwayne]

Fundamental recommendation: Buy and read Bracken's The Deep Sky Imaging Primer, Lodriguss's Catching The Light, or Richards's Making Every Photon Count.

Seriously. It's fulfilling to try stuff but you will  make better images sooner if you equip yourself with the prior-art science and engineering involved, much of which is not intuitive. Or at least  it wasn't to my brain, which is that of a software engineer originally trained as a photojournalist. For example you'll have a really good grasp of the Barlow question (well-explained here, to be sure!). You doubtless are familiar with signal/noise ratios but perhaps not with the sources of noise specific to astrophotographs and how to balance off the techniques for dealing with them. Or how to diagnose guiding and tracking problems. Or...well, read Charlie or Jerry or Richard for many, many more.

Edited February 1, 2023 by rickwayne

[jpoulette]

22 hours ago, iantaylor2uk said:

I would use it in equatorial mode rather than alt/az if you plan on taking photos.

Absolutely (alt/az is all I know - EQ will be a whole new thing!) - I will post a progress report below. Thanks! 😀

[jpoulette]

17 hours ago, Lee_P said:

It's great to see you're having a good time already reproducing my Askar FRA400 setup

......................

I recommend a ZWO 2″ Filter Drawer with M48 / M42 connections. (This one, but maybe you want to find a supplier local to you).

Lee - your write up on the FRA400 has been invaluable, and a good start for any absolute beginner .

Filter drawer ? Damn - I want one of those !! 😀

I saw a tutorial where the initial focus was being done with the mask. I though it interesting enough to get an inexpensive mask and give it a try just to understand the principal. I ultimately will use (and compare) the EAF auto-focus routine. it's all good.

I will include a progress report below. Thanks again for your help !

[jpoulette]

11 hours ago, rickwayne said:

Fundamental recommendation: Buy and read Bracken's The Deep Sky Imaging Primer, Lodriguss's Catching The Light, or Richards's Making Every Photon Count.

Seriously. It's fulfilling to try stuff but you will  make better images sooner if you equip yourself with the prior-art science and engineering involved, much of which is not intuitive. Or at least  it wasn't to my brain, which is that of a software engineer originally trained as a photojournalist. For example you'll have a really good grasp of the Barlow question (well-explained here, to be sure!). You doubtless are familiar with signal/noise ratios but perhaps not with the sources of noise specific to astrophotographs and how to balance off the techniques for dealing with them. Or how to diagnose guiding and tracking problems. Or...well, read Charlie or Jerry or Richard for many, many more.

I ordered Bracken last week - should be here soon. Thanks! 😀

The learning curve is steep, but not unreasonable. Why, just yesterday I learned the (real) difference between a "dark" and a "bias" frame. It amazes me how many different types of noise have to be compensated for.

But I suspect when you're "collecting photons" (where few exist) - that's life in the big city.

[jpoulette]

Progress report (from evening of 31 Jan 2023):

+15F and I'm outside with a freakin' telescope & tablet - I must be nuts.

Anyway - I picked up the lightweight 160mm pier and for a short refractor (like the Askar FRA400) it appears to work perfectly avoiding 'collision troubles'.

The set-up tutorials I've seen all say to pretty much articulate it as much as possible, before going into the field, to ensure there's no collisions or cabling issues. Regardless of the mount or load - I think one does not need to be told this as it seems like common sense to me.

As I'm still getting my sea legs on all this - I did my first focus check & alignment last night. (trial runs and I took me time of course):

Main camera focus took 5 - 3 second Baht exposures and ~ 15' to get the refraction spikes the way I thought were perfect.

On the alignment It took 10 - 3 second exposures and 20' to get it under 1' in both axis. I may have been a little picky - going back and forth a few times. The tracking threads on the mount could have been a finer ball-screw type pitch - but they're not terrible I guess. I suspect the more one does this the easier it will get. I may even consider replacing them at some point.

It was getting cold so I called it a night. All in all very happy with the ASIair interface and the AM5 in general so far. (But, of course, I haven't acquired any images yet....) Next steps will be to tweak the focus on the guider, and then acquire some data.

To be continued.

[rickwayne]

Excellent plan. I'm always in too much of a hurry to collect data and it has cost me.

[ollypenrice]

On 28/01/2023 at 13:11, jpoulette said:

 

I definitely understand the f-ratio and exposure time relationship (2x Barlow ~ 4x exposure time). I also have the Askar reducer (0.7x, f/3.9) and will probably start with that as well. I'll lose FL but as you suggest it will decrease exposure time quite a bit.

 

Jim

Have you come across 'The F ratio Myth' in astrophotography? It Googles and is worth your attention.  Briefly, your formula is clearly valid when a reduction in F ratio is achieved by increasing aperture but not when it is achieved by reducing focal length. In the latter case there is no increase in 'object photons.'

Also, plenty of giant professional telescopes have slow F ratios but capture images in astonishingly short times. That's because they have large pixel cameras in the back. What matters is not the F ratio but the flux per pixel - which goes up if you bin your pixels or use larger ones.

Software: In marriage, promiscuity is probably a bad idea. In image processing, it is a good one!    APP is very good and exceptionally good at making mosaics from panels which have had gradient removal and green bias removed in Pixinsight, after which a return to the civilized environment of Photoshop is much to be preferred - at least by me! I'll also dive into Registar fairly regularly. You can't beat an exotic processing love life...  On one thing, most of the imagers I know agree on this: Russ Croman has changed post processing forever with StarXterminator, BlurXterminator and NoiseXterminator. (I've put them in my personal order of importance.)

Olly

 

Edited February 2, 2023 by ollypenrice
Typo

[andrew s]

18 minutes ago, ollypenrice said:

What matters is not the F ratio but the flux per pixel - which goes up if you bin your pixels or use larger ones.

It even has a fancy French name @ollypenrice "etendue" 😊 

Regards Andrew 

[ollypenrice]

25 minutes ago, andrew s said:

It even has a fancy French name @ollypenrice "etendue" 😊 

Regards Andrew 

Indeed, though I thought there was a bit more than that to 'étendue' so I stuck with 'flux per pixel.' Doesn't étendue also have something to do with the efficiency of a light beam at a steep angle? Or something???? 🤪

Olly

[andrew s]

1 hour ago, ollypenrice said:

Indeed, though I thought there was a bit more than that to 'étendue' so I stuck with 'flux per pixel.' Doesn't étendue also have something to do with the efficiency of a light beam at a steep angle? Or something???? 🤪

Olly

It includes the size of the field as well if you want to get technical. Roughly it is the totally amount of light a telescope can capture. For the same aperture the scope with the larger field will have the higher etendue.  

Regards Andrew 

[jpoulette]

I wish I could help, but I took 4 years of French in high school and forgot every bit of it. 😎

[Adam J]

8 hours ago, ollypenrice said:

Also, plenty of giant professional telescopes have slow F ratios but capture images in astonishingly short times. That's because they have large pixel cameras in the back. What matters is not the F ratio but the flux per pixel - which goes up if you bin your pixels or use larger ones.

Yes, the point being that those giant slow professional scopes have massive sensors with massive pixels many many times the size of those used in hobby imaging.

However, I have to note that your flux per pixel also increases if you use a reducer. 

The overall problem with the Myth is that it will not take account of the reality that you have many more combinations of aperture and focal length scopes available on the market than you have sensors with different dimensions and pixel sizes. 

So in reality you have a choice if you want to image faster, You can try to find a sensor with larger pixels and or FOV (£££), or you can bin 2x2 the image at native focal length and increase your signal to noise that way, but you are also reducing your images total pixel count or you can use a reducer and have the same or slightly better effect and also increase your FOV at the same time. 

Finally swapping out a reducer / flattener to suit different targets is preferable to paying out for two scopes or alternatively paying for two cameras with different pixel sizes. 

There are also optical advantages to using a reducer to achieve a target focal length at a given aperture as opposed to negatively with a faster F-ratio optic. 

Adam

 

Edited February 2, 2023 by Adam J

[ollypenrice]

27 minutes ago, Adam J said:

 

There are also optical advantages to using a reducer to achieve a target focal length at a given aperture as opposed to negatively with a faster F-ratio optic. 

Adam

 

Sorry, I'm not with you on this. A target focal length at a given aperture does not allow for any variables so what are we comparing with what?

Olly

[Lee_P]

Specific advice here for @jpoulette -- one of the things that makes the Askar FRA400 a neat little 'scope is that there are no backfocus requirements; so long as the image is in focus, the backfocus is automatically correct. However, if you use the reducer then be aware that you will need to get your backfocus just right (probably 55mm or thereabouts) otherwise you'll get streaky corner stars. I'm not saying don't use the reducer, but it's just something to be aware of. Speaking personally, I never used a reducer with my Askar FRA400. 

Regarding "fast" optics in general, I try to sidestep the whole issue by treating astrophotography as a marathon rather than a sprint. My previous 'scope (the FRA400) was f5.6, and my current 'scope (Askar 130PHQ) is even slower, at f7.7. But *shrugs* it's fine, I just keep plugging away until I collect enough data. Granted, I might change my mind on this topic if I ever use a speed demon like a RASA 😁