Lunar Imaging with Ritchey–Chrétien - Forums

Topic starter

May 18, 2024

If I am using an 8inch RC telescope with 533 to image the moon, and the FL is only 1625mm and I want it to be more up close, is it ok to use a triple Barlow?

Or will it degrade the image too much?

Also, how many frames should I be aiming for with 533?

5000? 10000? 20000?

Also, out of all those frames, what percentage should I stack? 10%? 5%? or less?

Thanks

Georges

May 21, 2024

Hi
Sorry for the delay, but I've been having some issues lately… …Here are some recommendations for the Barlow:
First of all, to know the right sampling, and to know which barlow to take, here is the formula:
E=206 P/F
P=pixel size
F=focal
In your case: E=206x3.76/1625 = 0.47

separating power: PS=120/diameter
in your case PS=120/203=0.6

Ideal Sampling = Ps / 2 = 0.3

So you can add a barlow of 2 … => E=0.6

Afterwards you can always take more, but you need good weather conditions…

Here is a web page (in French) on the practice of sampling..
https://www.univers-astro.fr/fr/content/6-le-calcul-d-echantillonnage

Then for the number of images: it depends on the targeted object and the FPS of the camera in relation to the histogram:
for example:
for the moon in large format: 360s exposure time for an FPS of 80 frames/s
for Jupiter which has a rapid rotation:
90s exposure time for 100 frames/s
for Saturn:
180s exposure time at 100 frames/s
….

You should also know that for the planets, you can use the winjupos program which allows you to assemble several images by derotating them. Practical for Jupiter, Saturn and Mars…. For a more beautiful image in the end.

Finally for autostakkert, favor the fewest images possible (1%, 3% or 5%) depending on the quality of the sky that evening and the videos because the definition will only be better..

Sincerely
Georges

Helpful

Alien_Enthusiast

Topic starter

May 21, 2024

Hi
Sorry for the delay, but I've been having some issues lately... ...Here are some recommendations for the Barlow:
First of all, to know the right sampling, and to know which barlow to take, here is the formula:
E=206 P/F
P=pixel size
F=focal
In your case: E=206x3.76/1625 = 0.47

separating power: PS=120/diameter
in your case PS=120/203=0.6

Ideal Sampling = Ps / 2 = 0.3

So you can add a barlow of 2 ... => E=0.6

Afterwards you can always take more, but you need good weather conditions...

Here is a web page (in French) on the practice of sampling..
https://www.univers-astro.fr/fr/content/6-le-calcul-d-echantillonnage

Then for the number of images: it depends on the targeted object and the FPS of the camera in relation to the histogram:
for example:
for the moon in large format: 360s exposure time for an FPS of 80 frames/s
for Jupiter which has a rapid rotation:
90s exposure time for 100 frames/s
for Saturn:
180s exposure time at 100 frames/s
....

You should also know that for the planets, you can use the winjupos program which allows you to assemble several images by derotating them. Practical for Jupiter, Saturn and Mars.... For a more beautiful image in the end.

Finally for autostakkert, favor the fewest images possible (1%, 3% or 5%) depending on the quality of the sky that evening and the videos because the definition will only be better..

Sincerely
Georges

Thank you for all the info! I will note it down!