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Newbie w/ Meade LX200 10" ACF and ASI071MC Pro and ASIAir Plus


DBasinger

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Guess I started backwards by buying the LX200 10" ACF not knowing what I wanted to do  and THEN  deciding to do imaging.

Now, I have moved my LX200 10" ACF (with 0.62x reducer) from the fork to Celestron CGEM II  Equatorial mount, with StarSense and GPS.

My cameras are ASI071MC Pro for DSO and ASI120MC for Guider, using ASIAir Plus for initial capture, etc.

However, I'm very, very new to imaging! So, with this setup, what should my early exposure times and number of frames be for objects like Orion Nebula and Andromeda, i.e. larger and brighter objects?

As I go to smaller and dimmer objects, how should I adjust my exposures and number of frames?

 

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yes that's a bit of a beast to start imaging with!  There's never a "right" answer to what exposure time you should go for, but there are certainly "wrong" ones. Essentially the key thing is to make sure at a minimum exposure the sky "noise" overwhelms the read noise of the camera, and at a maximum that no details are blown out. Obviously this varies greatly between different scope / camera combinations.

First thing is to sort out the best Gain and Offset for the camera. I don't have an ASI071MC Pro, but I'm sure there are threads you can find here or on Cloudy Nights that will discuss this.

I'm sure there are better ways, but I used the spreadsheet referenced here - http://www.gibastrosoc.org/sections/astrophotography/optimum-exposures-calculator - to work out an "optimum" exposure background ADU figure for my cameras (for a given Gain), and found this helpful (I think it's probably best treated as a minimum really).  You need a median background ADU figure from a calibrated image to use it (in particular so that the bias is subtracted), but can work backwards from that to get a figure for an uncalibrated frame. From there I just use this ADU figure as a reference when imaging (I use NINA for imaging, which will tell me the median ADU of each image, which won't usually be too far off the median background). Many targets I can go longer if I want, but it does depend how bright they are.  Longer exposures demand more of the guiding as well. Experiment and see what works for you is the other thing of course.

How many sub-exposures depends on how long you've got! The more the better, albeit with diminishing returns. But in general terms it's the total imaging time that determines the quality of the end product.

This presentation by Robin Glover is more than useful to understand some of the issues around exposure times and numbers

 

 

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  • 6 months later...
On 15/02/2022 at 18:29, DBasinger said:

Guess I started backwards by buying the LX200 10" ACF not knowing what I wanted to do  and THEN  deciding to do imaging.

Now, I have moved my LX200 10" ACF (with 0.62x reducer) from the fork to Celestron CGEM II  Equatorial mount, with StarSense and GPS.

My cameras are ASI071MC Pro for DSO and ASI120MC for Guider, using ASIAir Plus for initial capture, etc.

However, I'm very, very new to imaging! So, with this setup, what should my early exposure times and number of frames be for objects like Orion Nebula and Andromeda, i.e. larger and brighter objects?

As I go to smaller and dimmer objects, how should I adjust my exposures and number of frames?

 

Hi
I did watch Robin's video a few years back - very good indeed.
I have an old LX200 Classic 10" - I am old too (!), which 0.62x reducer are you using?
I did add the Skywatcher 10:1 focuser and that adds a minimum of 90mm from original prime focus and I wish to find a 'decent' 0.62x or near that can be fit after focuser (not the original Meade/Celestron...) and hopefully not braking the Bank too.
I am not in search of perfection, but a 'doable' one.

The intention is to fit LX200 onto wheeled Tripod and leave it on to use as Planetary and Deep Sky + add a small refractor on top when in use, getting too heavy for me!

Thanks
M

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I assume you're guiding through an Off Axis Guider for that long 1570mm focal length.

A colour camera is sometimes not sensitive enough for OAG use, how are you fairing ?

The guiding pixel scale is 0.62arcsec/pixel.

If you had the mono version you could bin that to a more sensible 1.24arcsec/pixel, and the increased sensitivity would help too.

Michael

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On 15/02/2022 at 18:29, DBasinger said:

Guess I started backwards by buying the LX200 10" ACF not knowing what I wanted to do  and THEN  deciding to do imaging.

Now, I have moved my LX200 10" ACF (with 0.62x reducer) from the fork to Celestron CGEM II  Equatorial mount, with StarSense and GPS.

My cameras are ASI071MC Pro for DSO and ASI120MC for Guider, using ASIAir Plus for initial capture, etc.

However, I'm very, very new to imaging! So, with this setup, what should my early exposure times and number of frames be for objects like Orion Nebula and Andromeda, i.e. larger and brighter objects?

As I go to smaller and dimmer objects, how should I adjust my exposures and number of frames?

 

Looking at your equipment you've given that learning curve a steeper trajectory.. are you going to fit Orion in the frame? Certainly not for m31

Can the cgem perform at under your image scale at that fl?  Seems like a tough ask

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