Planning my first PST mod and need some help

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Re: Planning my first PST mod and need some help

Post by solarchatted » Sun Aug 25, 2019 3:25 pm

This is not exactly a great image - I actually managed to achieve something very similar just with the PST!
Taken this morning using AR90/900 with AR102 focuser + PST SCT mod [see other posts] + D-ERF [kindly sold to me by marktownley] Binning 2x - Altair 178M [if necessary, a 174M -I cannot afford it now - it will be a while].

I will check other takes if are better than this one.
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Astronomo.space - AR90/900 test
Astronomo.space - AR90/900 test
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Re: Planning my first PST mod and need some help

Post by marktownley » Sun Aug 25, 2019 4:10 pm

That looks to be working well Mauro!


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Re: Planning my first PST mod and need some help

Post by solarchatted » Sun Aug 25, 2019 5:17 pm

1. I noticed a bit of a shine on top right of image - the next in particular.
2. would a tiny 40mm fan create too much turbulence - to fit on top of the tube in between front lenses and D-ERF ?
They are separate at about 20cm, maybe a little more

Maybe the D-ERF is shining to the back of the front lenses or simply on the eyepiece side something is not right.

This is another image and then I am going to watch TV and rest ... this image is from this morning, I need to check yesterday videos to see if this one is better - but I doubt - cloudy and hazy!
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Supposed to be North side - yesterday I believe it was more prominent ...
Supposed to be North side - yesterday I believe it was more prominent ...
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Re: Planning my first PST mod and need some help

Post by marktownley » Sun Aug 25, 2019 7:41 pm

Nice addition, using a flat field will even things out considerably and give big improvements.


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Re: Planning my first PST mod and need some help

Post by solarchatted » Mon Aug 26, 2019 3:07 pm

1.
I am now wondering which camera will be best with my setup - best as in pixel matching camera lenses:
174M 290M 178M [mine] or what?

2. which Barlow ? Just the Expensive PowerMate x2.5 ? I see that the cheap Chinese x5 Barlow I used nearly did the job [metal one, not plastic]

3. Filters? I tried ' once ' my Meade 4000 #25 but no difference visible to the eye - although with my PST I did notice a difference.

4. I guess I will be forced to get a BF10 in the future!

5. I do own a Orion 2" 0.8x Reducer Flattener which works very well with AR152 on Deep Sky images, can I use it here to get full disc using the 178M?
Even if, maybe it is not enough to reduce - I also have a 0.5x GSO 2"

Once again, when I can afford it - in the future ...

I hope it is OK, to keep this thread going - I do not wish to breach any rule.
:bow

It is becoming a one page for Newbies !
Attachments
AR90/900 PST mod Barlow x5 Altair 178M 2x Binning 800x600 ROI
AR90/900 PST mod Barlow x5 Altair 178M 2x Binning 800x600 ROI
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Re: Planning my first PST mod and need some help

Post by marktownley » Sat Aug 31, 2019 3:41 am

Hiya Mauro,

You're not breaching any rules, don't worry!

To address your points:

1) - I think for now using the 178M binned is a good option - 2,4um pixels binned gives you effective 4.8um pixels which is a nice size, this will give you more light and keep the exposure short, and will also give you more fps, which, noticing you are using ROI will help more. Personally I would stick with this setup, as you get more experienced with capture and processing your images will improve, just throwing a new camera at it will have little effect at this stage.

2) Seeing is never as good as we like it here in the UK, stick with the 2.5x powermate, when I used to PST mod I found this to be a nice scale, you'll see Stu regularly uses a 2.5x powermate with his 150mm home made scope. 5x you are pushing the focal ratio up >f50, which is rather high and doesn't work with the pixel size. The 5x barlow will unlikely render any more detail than you get with the 2.5x, just larger image scale - you can always increase image scale in post processing to the same effect.

3) Where are these filters going to go and what do you want them to do? The DERF, ITF and blocker from the PST is all you need.

4) No rush! Cut your teeth on the BF5, this is what many have done before you!

5) No such thing as a free lunch with a PST mod - you might well get a full disk fitting on the chip, but you will find it shows a huge sweet spot (only a quarter of the disk will be on band), use the etalon in regular PST mode at 40mm for full disks. Larger aperture PST mods are for higher resolution shots not full disks!

Coming to the questions in your previous post:

1) Reflections come with the territory with PST mods sometimes, the cure is systematic trial and error to identify the source and rectify it.

2) I honestly don't think you need a fan, you are running at 90mm aperture with a 70mm sub aperture ERF, you will be fine. It's just another complication that's not really needed. I have a fan on my 8" SCT that I use for Ha - does it make any difference when it is on? No, I don't think so.

Looks like your pretty much there with the mod Mauro, improvements in post processing is what will take images forward now.

Mark


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Re: Planning my first PST mod and need some help

Post by solarchatted » Wed Sep 04, 2019 4:37 pm

Thanks for the useful inputs - I like to learn and I agree, there is no difference in going to small using ROI - at least with my camera set Binning to get to 4.8µm - the 178M is quite efficient/reactive to light at I believe 75% QE.

This morning I had a quick section, knowing it would cloudy up and it did!
I just felt a need to observe The Sun after I missed Saturday/Sunday due to be fixing two Home Windows Computers!

I was stunned how beautiful is the view now!
Then I thought, lets get the camera out and try.

I only managed 2-3 videos, one image here - I will try and see if other better.

By the time I was ready, clouds started to sporadically pass until it covered up as expected.

NOTE: maybe it is leftward - the spiral !
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2019SEP04SUNAR90SBiCentre01F.jpg
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Re: Planning my first PST mod and need some help

Post by Merlin66 » Thu Sep 05, 2019 1:43 am

Mauro,
Excellent result.. Well done!


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"Imaging Sunlight - using a digital spectroheliograph" - Springer

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Re: Planning my first PST mod and need some help

Post by solarchatted » Sun Sep 08, 2019 9:35 am

Strangely enough, my home made PST eyepiece adaptor can be use as a tilt adjuster!

Having modified the Chinese 2" to 1.25" adaptor - taken out the internal metal ring and drilled another hole/threaded and replaced thumbscrews with nylon ones at 120° I can now just tilt the needed side and get rid on ringing and shining.

Today for the first time I can get a sharper video - I noticed the weather might be slightly better than usual - having had a clear night.

Just testing it and taking videos to see the result, but I guess it will be much better as it is very clear on laptop monitor already.

Learning as I get along.

I cannot thank enough all that helped me to get there and particularly Mark Townley !!

I will post images when I can.


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Re: Planning my first PST mod and need some help

Post by solarchatted » Wed Sep 18, 2019 10:28 am

Tilt adaptor would be better of course, but at present it seems that simply raising gain to over shine camera, then tilt the PST eyepiece holder with the 3 thumbscrew modified Chinese 1.25" to 2" adaptor does the job.
I tried last time at the end of my learning session and it did clear the whole image ... much sharper - I guess I am now in the fine-tuning stage.

On another matter and it is not for the moment, but which camera would anyone of you suggest I use with this AR90/900 + PST Etalon mod?
I do understand at some point - probably - the next expense will be to get a BF10 ... then another camera more suited for this setup - i.e. pixel / FL matching.

Just trying to get the best out of my cheap setup.

Once again, although a 'very' long time ago I did an electronics course and in it there was a 'very short' explanation of colorimetry and a camcorder functions with some optical basic explanation [just a few pages] and also read a Photography 'How to a long time ago', I am not really an expert on optics!

Too cloudy today - just my usual luck on my day off and alone in the house for the whole day and I cannot use the time!

I might have to take up again music making and dust clean my old programs still work on Windows 10, although I was seriously thinking on 'also' do 'Radio Astronomy - I used to be in radio communications [Repairing them] and might get back to my old filed -I guess would also be interesting for Solar!

I am trying to slowly prepare for retirement ... still a long time ... and have an idea of what to do and then get rid of all the gear I do not use!


Thank you
Mauro

ADDITION:
Had a quick look on ' CCD Suitability Calculator ' and it seems the 174M is a actually the best, because to obtain the ideal sampling I need to 2x binning with both 290M and 178M to reach 1.33 and 1.1 Resolution respectively, while the 174M gives you 1.34 without binning.

I am wondering if it really is really worth spending for a 174M, or use binning with 178M


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