Lucky imaging: in need of tips before I start - Forums

Topic starter

May 10, 2019

Hello Everyone,

summer is coming here in the Netherlands and the nights are getting shorter and brighter. I thought that this could be a good occasion to take out my C11 (2 years unused .. shame on me!) change my main imaging camera to the ASI290MM and start doing some unguided lucky imaging on small planetary nebulae.
I did a lot of planetary imaging in the past so I have some experience in the matter and I would like to know what is different. For instance should I still calibrate the frames with darks and flats if my exposures will be probably betweem 0.1 ms and 2 sec?
What type of gain is best for lucky imaging.. lowest read noise?
Should I focus on LRGB filter only or lucky imaging is also possible with NB filters?

Any other tip that comes to your mind is welcome!
Clear Skies,

Andrea

Engaging

Michael Caller

May 10, 2019

HI Andrea

Thats a good question regards calibration frames at such short exposures, are you imaging planets or deep sky images?

I have a ASI 1600MM and shortest exposure I use on LRGB is 60dec and always use calibration frames, I do not use Bias frames I replace these with dark flats , basically shoot flats at the same exposure length as your flats but with the cap on. remember each filter need their own flats (LRGB & Narrowband)

APT and SGP both have flats aide which is very good tool for getting the best flats , set APU between 20,000 - 25000, field flat generator will also give you best flats you can purchase one or make one , I purchased one for £200 from Astoshop.eu

Gain settings can vary I use 139 Gain at 21 offset for narrowband and 75 Gain and 13 offset for LRGB , however an all good rounder is 139 gain, light pollution can play a big part, with the ASI290 you can keep the exposures short giving you low noise.

With the ASI 1600MM my exposures are between 60 - 180sec, shorter exposures but more of them. remember when imaging LRGB luminance has more detail therefore I aways shoot more luminance.

For example if im shooting 5 hours during one night I would set up for 40x180(L), 20x180(R), 20x 180(G) & 20x180(B), however on shorter nights in summer I only shot over multiple nights, if possible I will shoot narrowband only on any nebula thats high, which is very hard to find at this time of year, Rosette nebula is a good DPO to go for.

This time of year is classed as galaxy season so providing you have a large focal length you can get some nice details of M45, M51, M81, M82, M101 at this time of year.

Also the moon can be a spoiler , when the moon becomes a issue for light pollution I only shoot narrowband leaving LRGB for new moon.

Check your filters and make sure they are Parfocal, otherwise you will need to focus each filter during an imaging session , not to much hassle if you use Focus stepper motor and SGP, but without it it can be a long night, some people don't bother but makes processing very difficult getting sharp stars.

I am very new to Astroimaging but this is what I have learnt so far, learnt them the hard way :-)

Hope this helps.

Helpful

KuriousGeorge

May 10, 2019 · Edited: May 11, 2019

You may not need darks and bias due to short exposures. But it wouldn't hurt. If you're shooting bright nebula or planets, flats not needed. But if you're going for wide shots of very faint object like tidal streams, you'll need flats for highest contrast.

BTW, IMHO, this is one of the best examples I've ever seen of lucky imaging. Many thousands of 1-sec exposures and keep only the best FWHM…

http://www.astrobin.com/379283/B/

Helpful Concise

Jeffbax Velocicaptor

IOTD Staff

May 11, 2019

Hello,

On my opinion 290MM is the best mono CMOS for short exposures so far. You shoiuld push the gain at 80% (500/600) and offset at the maximum.
Biais and flats are not mandatory, but darks are. If your camera is not cooled, you have to make different series of darks to match the temperature (tolerance is 1°C).

For stacking, SIRIL is very good.

You can find some examples in my gallery.

Clear skies.

JF

Helpful Concise

Andrea Alessandrelli

Topic starter

May 11, 2019

Thanks everyone for your answers!

Jeffbax Velocicaptor:
Hello,On my opinion 290MM is the best mono CMOS for short exposures so far. You shoiuld push the gain at 80% (500/600) and offset at the maximum.
Biais and flats are not mandatory, but darks are. If your camera is not cooled, you have to make different series of darks to match the temperature (tolerance is 1°C).

For stacking, SIRIL is very good.

You can find some examples in my gallery.

Clear skies.

JF

My camera is not cooled and my plan was to use firecapture to capture an AVI file starting with 1 sec long exposure adjusting the gain for every filter and keeping an eye on the histogram, as I always did for planetary. Thou this would make dark calibration a mess because I would need to take darks for each gain setting I used.
So I think i'll try to capture an AVI at a the same gain/offset for every filter (thanks for the tips on the settings, i'll try them out) and then when the "round" is over put a cap on the scope and take a dark AVI, temperature shouldn't differ much if I do it like this.
Then I thought I could use autostakkert to evaluate the quality of frames and export them as fits for proper calibration with any given program (Pixinsight one of them). About this does SIRIL works on fits only or also AVI files?

And by the way, your lucky imaging pictures are great!

Michael Caller

May 11, 2019

It's a shame you haven't got a cooled camera as you could create a calibration library which you can do anytime and replace every few months

Andrea Alessandrelli

Topic starter

May 11, 2019

Michael Caller:
It's a shame you haven't got a cooled camera as you could create a calibration library which you can do anytime and replace every few months

Yeah I know... I bought it together with the ASI1600MM-Cool to use it as guide camera and for planetary. I never thought of lucky imaging on DSO before recently otherwise I would have bought a cooled one

Jeffbax Velocicaptor

IOTD Staff

May 11, 2019

Instead of AVI, SER is lighter.

AS!3 will have problems to evaluate DSO images quality (tried it for months). SIRIL has a very efficient FWHM quality sorting tool. It works with SER files.

Good tries

Andrea Alessandrelli

Topic starter

May 11, 2019

Jeffbax Velocicaptor:
Instead of AVI, SER is lighter.AS!3 will have problems to evaluate DSO images quality (tried it for months). SIRIL has a very efficient FWHM quality sorting tool. It works with SER files.

Good tries ;)

JF

I will try out SER and of course SIRIL, thanks for the tip! Now I have to wait for good seeing

Clear Skies,

Andrea