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From DSO to planetary - long list of questions

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#1 FredOS


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Posted 16 September 2020 - 06:22 AM

Hello, I have been doing DSO for some time with reasonably good success but would like to start planning for planetary equipment. I image in France which means Mars is OK but Jupiter and Saturne a few years away if I want those targets to be above 40 degrees. Bortle 5 skies.

I have a very good mount : 10Micron HPS 2000 which I use unguided. On top, a Planewave CDK12.5 (F8 at FL of 2650mm) and a focuser/rotator (Nitecrawler). in my tool kit, I already have a powermate X2.5 from Televue. I also have a ASI1600 mono camera (3.78 microns) which I could replace with a dedicated planetary camera. I would plan to continue with mono camera and filter wheel.


So questions :


1) In DSO world, we do flats to correct for optical issues (vignetting) and dust on camera or filter wheel. As far as I can tell, no flats in planetary / video world. I can see that optical issues are not a problem but why so for dust. Is it because of strong SNR or do people jus maintain dust free equipment ? Does it make sense to calibrate with a flat frame on your final stacked image ?

2) In planetary world, focusing seems a manual exercise (look at the video and adjust - use your eyes). In DSO, we have automated software that targets the smallest FWHM of stars to provide good focusing. Would it make sense to use such a routine before targeting a planet or does planetary require this added amount of precision (that your eyes provide ?)

3) The Planewave holds collimation very well. I have read that for planetary, re-collimation is suggested systematically. Is that really needed with a CDK type of design ?

3) Filters :

2.1). It is unclear to me if there are benefits to LRGB vs RGB assuming one uses an ADC. Is there a consensus view (I have read, use LRGB only if excellent seeing). Can the L filter be used for better focusing ?

2.2). What would be a good list of must have filters : L, R, G, B, W47 (for ADC adjustment), ?, ?. For Moon, same / different ?

4) ADC :

4.1) I understand an ADC remains recommended for Mono. Is that still the case if the target is in the 40 -55 degree range ?

4.2) Most ADCs appear to have a T2 connection (one male and one female). Does it matter which side you use (i.e. does a side of the ADC need to be connected to the telescope side or can you reverse this).

4.3) List of manufacturers appear to be Zwo, Pierro astro, Astro Systems Holland, GreatStar ADK (more expensive), Gutekunst (very expensive). Any views on the relative merits, ignoring the Gutekunst one.

4.4) With ADC and mono, I understand that an option to adjust the ADC is to use a W47 filter. Is that confirmed as a practical solution ?

4.5) I understand the ADC needs to be oriented to align mid point with horizon. My focuser can also rotate full 360 degrees so I assume I could use a screw in connection and just adjust the rotator when I need to align the ADC ?

4.6) I read somewhere that I should also consider having the flexibility of rotating the camera in relation to the ADC. What would be the point of that if the camera is aligned to the ADC "mid point"

4.7) From the DSO world, I would normally have considered the following imaging train : filter wheel > ADC > Powermate > camera. There seem to be long posts on this topic of Powermate before or after ADC. Is there a consensus view on this considering my equipment ?

4.8) Some are also recommending to have the filter wheel just before the camera. However, If I was planning to use a W47 filter, I assume it needs to be before the ADC ? 

5) Software :

5.1) I could be wrong but it appears that deconvolution is not part of the tool kit. Would it make sense to take a few frames of stars next to target, extract the PSF and use deconvolution software (such as in pixinsight)

5.2) Winjupos. It has an option to "integrate" R,G,B frames. When doing LRGB, do you mix L and RGB outside of Winjupos after "aligning" in winjupos ? On Winjupos, i'm a bit unclear on what the LD adjustment does and how to use it (any good tutorial ?).

5.3) AS3. consensus seems to be to not bother with measuring frames but to output different % (25, 40, 60) of best frames and compare the results. Am I correct ?

5.4) Winjupos. How does one use it when you are also capturing a moon that is in transit (before Jupiter for example). I cannot imagine it works with a series of AVIs spread over 15/20mn as the moon will have moved to a different reference point in relation to your target.

6) Anything else I should have asked ?


Thank you for taking the time for reading and providing responses if any and sorry for the long post...


#2 Tulloch



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Posted 16 September 2020 - 06:37 AM

Hi Fred, that's a lot of questions :)


I would start by watching these tutorial videos, I'm sure a lot of your questions will be answered...




#3 leviathan


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Posted 16 September 2020 - 06:58 AM

1) No need for flats in planetary imaging, just keep your tiny planetary sensor and filters/barlow dust-free;
2) You can still use Bahtinov mask to precisely focus, but at long focal length and variable seeing it will change during the night. So better to focus on details of Moon/planets;
3) Doesn't hurt to check collimation every time at the beginning of imaging session. Precise collimation is a key in success at imaging at long focal length and tiny details on planet's surface;
2.1) No need for L channel in planetary imaging;
2.2) RGB, UV, IR-pass (several nanometers long from different companies like Baader 685+nm, Astronomik 742+, etc.), Baader 610 Red longpass was also used for Uranus, Methane band. Maybe I forgot something ?
4.1) Yes, ADC is pretty much must have up to 60-70 dgr. above horizon where atmospheric dispercion effect is already small;
4.2) Not sure which ADC model do you mean, but ZWO is pretty much straight forward to put into the telescope. :)
4.4) Better use color camera or visual/eyepiece to control;
4.5) Yes, just make sure that bubble level is spot on;
4.7) DO NOT use barlow after ADC ! Otherwise it will increase aberrations of ADC's prisms. Correct imaging train is: Powermate > ADC > filter wheel > camera.
4.8) I would always use filter wheel just before the camera;
5.1) Deconvolution is very strong tool in planetary post-processing and lots of folks are using it. In fact (I might be wrong, but) planetary imagers started to use deconvolution long time before DSO imagers. :)
5.2) Again, no need for L (in classic understanding) filter. However, you can use IR as L in some cases. As for WinJupos, I normally de-rotate every channel separately, then combine RGB together;
5.3) Yes;
5.4) Goal is to shoot short videos or de-rotate videos in WinJupos. Program can recognize moon in transit, you'll see it for example in case of Jupiter;
6) Many, many other questions are going to come. :)


Phew, that was a LONG list. grin.gif Please don't take my answers as a 100% guide, I'm still learning myself. smile.gif

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#4 FredOS


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Posted 16 September 2020 - 09:00 AM



thank you for the detailed response.

on 2.1) IR pass filters, is there some good reading on the benefits of 685nm vs 742, etc...

on 4.2). Interested also for non ZWO if there is a right / wrong side. I could always check with the manufacturers

4.4) I don't plan on using a color cam so interested on the views of others on how effective W47 filter is for ADC setting for mono

4.8) If filter wheel is just before camera (and after ADC), interested in the views of those using a W47 filter if this will be an issue.


Thank you

#5 leviathan


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Posted 16 September 2020 - 09:35 AM

for IR - it all depends on the target, seeing conditions, camera sensitivity and so on. Ideally you would need to keep 2-3 of them for Uranus, Moon, Jupiter, Mars, etc. Just check here and on Astrobin who is using what.


I will leave others to answer non-ZWO ADC and W47 filter question as I have no experience there.

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