Pikon and settings for godd images

You might get more help from your local amateur astronomy group, particularly if they have members who build their own telescopes and/or grind their own lenses, than here.

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Martin    | martin at 
Gregorie  | gregorie dot org

In Nachricht Martin Gregorie haben Sie geschrieben:

Hallo,

or just try an astronomy-site like e.g.

, or similar. Just find the search-field and type "raspberry camera" or something like this into it. And BTW the people in those forums are very likley to help you.

Greetings, Juergen

Den 2020-10-25 kl. 01:06, skrev snipped-for-privacy@freakmail.de:

I thank you both for your suggetions. I'm a bit surprised to see that noone is doing astrophoto in this group though.

My guess is that they either use commercial shiny (Celestron or equivalent and strap a good Nikon DSLR onto it) or they grind their own mirrors and make tubes/equatorial mounts etc themselves, both because they can and because its another part of astronomy that they enjoy.

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Martin    | martin at 
Gregorie  | gregorie dot org

declaimed the following:

Have you verified that you still have focus movement available when trying sky objects? The closer an object is, the more the sensor has to be "pulled out" of the tube. Objects at infinity should have the sensor as far in the tube as possible.

Second -- how long are the exposures?

If my math is correct, celestial objects "move" ~15 arcsec per second, even a 1/4sec exposure well encounter nearly 4 arcsec of movement if you don't have an equatorial tracking mount on the telescope.

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	Wulfraed                 Dennis Lee Bieber         AF6VN 
	wlfraed@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/

when

second,

Another factor is diffraction: the PiCam HQ at 38mm square is relatively large compared with the primary mirror at 11% of total the aperture. That's not including the mount and with 3D printed support legs, which will be relatively thick, so at a guess you'll be starting to see diffraction effects from them as well as reducing light gathering ability. This combination will tend to soften the focus as well as reduce light gathering ability.

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Martin    | martin at 
Gregorie  | gregorie dot org

Den 2020-10-25 kl. 17:09, skrev Dennis Lee Bieber:

Yes - focus is good. I hook it up to a tv (shooting from an open window in a dark room) I can see when I gt in and out of foucs. The stepper makes the movement _very_ fine, and that is needed. It is difficult to turn the knob by hand and get it sharp. Hence motorized.

Collimation is good too - printed a tool to help that fitted a laser to help out.

I do not have tracking - yet. But that is part of whats fun with a pi (and 3d-printer). I control the elevation but not the azimuth. And I tried both taking pictures in burst mode, in slower mode, and filming. I used the film to feed PiPP (amazing thing that finds the planet and center it in the pictures) and then I feed the output to AutoStakkert .

But hmm, I think I need to try more options in those tools. I fed it 2 40-50 secs of video but well - it perhaps needs more but said it was about 1400 pics which gives ca 30 fps which is short. like

33 ms. In that time the planet move from the edge of the screen to the other edge. and it is small - like 50 by 50 pixels. sizewise it looks like a tray icon moving.

I lurked a bit on the sites given as suggetions and it looks like my approach is correct. I perhaps need more patience.

Den 2020-10-25 kl. 14:25, skrev Martin Gregorie:

Yes - I would have thought that many here would fit into the second category :-)

Try Polaris, nearly no movement.

Greetings, Kallu

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Have a nice day <

declaimed the following:

Alt/Az mounts will add another complication -- image rotation. From a quick read of the software web site, I can't tell if the stacking software applies corrections for image rotation. I believe the software that came with my (archaic these days) Meade Lunar-Planetary Imager (monochrome) and Deep-Sky Imager (color) does apply rotations if needed -- haven't used them in 20 odd years (I need to find new battery holders that fit the arms of the 8" SCT).

An equatorial mount, if reasonably polar aligned, only requires tracking in right ascension (east/west) as the declination (north/south) of an object doesn't change as the night goes on. No rotation of objects in the view.

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	Wulfraed                 Dennis Lee Bieber         AF6VN 
	wlfraed@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/

Den 2020-10-26 kl. 01:02, skrev Dennis Lee Bieber:

Hmm, yes. Thanks for the pointer

Is that true also for planets? I get that it correct for stars and deep sky objects, but planet evolve around the sun, not polaris

As you may have noticed - I am a novice in this field.

declaimed the following:

The problem is that the EARTH is what is rotating. When you polar align an equatorial mount, you line up one axis with the axis of the earth. In that configuration, while the earth is rotating in one direction, the telescope is rotating in the opposite -- and since the axes are parallel, any distance above/below the equator stays the same (so no adjustment needed in declination).

Using an alt/az mount means you have no axis parallel to that of the earth (unless you set up the telescope at either the N or S pole itself!). As you follow objects across the sky, the two axes of the telescope keep changing orientation relative to the object. Difficult to illustrate in a text-only medium but...

That equatorial mount, on the equator, will appear to the user to be completely on its side.

)|

(where ) is the curve of the earth, and | is the RA axis of the scope). In contrast, the alt/az axis will be

)--

and there is no way to point a scope tube at the end of that axis that can compensate for earth rotation.

Due to so many scopes now being sold with alt/az mounts (for visual usage, the computer controls on these models is able to track both alt and azimuth) there are

which are motorized to compensate (ignore the William Optics entry -- from what I see that is a manual rotator which means you have to nudge it during the exposure; more suited for easily rotating a camera so the long side of the sensor fits the object better).

More information than you care for at

along with the embedded linked articles.

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	Wulfraed                 Dennis Lee Bieber         AF6VN 
	wlfraed@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/

Den 2020-10-26 kl. 15:26, skrev Dennis Lee Bieber:

Many thanks - I'll look into the links