Lunar imaging – does it need a flat field?

[Dawson]

For planetary imaging, generally so little of the chip is used for data acquisition that it doesn’t matter if the field is flat or not. But for lunar imaging, using most of the chip, does a flat field improve things, or does the stacking process mean it makes no difference? I can’t believe I am only now just thinking of this question.

James Dawson
Nottingham

[Grant Privett]

I would say that, ideally a flat is needed for lunar and planetary observing.

Yes, stacking will help to hide any dust doughnuts present and – depending on how the stacking is done – even vignetting, but the final result will normally be better if flatfielding is done.

And don’t forget that flat frames need their own darks, even with CMOS sensors – as bias offsets may be present in the image.

[David Basey]

Hi James,

This video is a lengthy interview/tutorial on AutoStakkert! with it’s creator Emil Kraaikamp. Around the 1h26m mark there is a discussion on using the calibration features within AutoStakkert!. Mostly the discussion is about deep sky stacking but flat fields for Solar System are briefly mentioned.

In summary, the view is

• Solar: definitely
• Lunar: pretty definitely
• Planetary: don’t bother

David.

• This reply was modified 3 weeks, 3 days ago by David Basey.
• This reply was modified 3 weeks, 3 days ago by David Basey.

[Dawson]

Thank you both. I have not been clear, sorry, I’d had two glasses of vino! I agree, a flat field calibration frame is definitely helpful for lunar imaging.

I meant should I use a field flattener, to project a flatter image on the chip when taking video for stacking of the Moon? Or again does the stacking process negate the need?

James

[Mr Giovanni Di Giovanni]

Hello James

I am very pleased that there are still people in the world who appreciate a glass of wine! I usually drink two glasses with spaghetti alla carbonara (an excellent dish from Rome), or spaghetti aglio olio e peperoncino (garlic, oil and chilli); three glasses with ‘arrosticini’ (sheep meat) from my village Civitella Casanova (I live at the foot of Gran Sasso). I would like to recommend Montepulciano d’Abruzzo wine, red or cerasuolo. Just think, one snowy winter evening, after gorging myself on about 30 arrosticini + brown bread and oil + tomato + well-aged pecorino cheese, all washed down with red Montepulciano (13°) and finally your excellent Johnnie Walker Black Label 12 years old, I didn’t feel cold all night as I spent it observing the Moon, Saturn and various nebulae. What a wonderful memory.

Cheers to everyone!!

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