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Bias frames


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2 hours ago, TerryMcK said:

Excellent thanks - this is where I get confused as the article says the bias frames should be taken at the same temperature as the lights...🤔

 

"BIAS FRAMES

A bias frame is an image taken with no light falling on the image sensor, using the shortest exposure time you can manage with your camera. Either close the shutter or cap your telescope. Bias frames should be recorded at the same temperature as your light frames (the actual exposure of your target), and using all the same camera gain or ISO settings"
 

Edited by PeterBolt
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It is best to take bias frames at the same temperature as the lights. That what I used to do when using DSLR and it works well.

However most modern dedicated astro CMOS cameras don't need bias frames as just darks work well. Bias frames can give issues and are unnecessary.

Flat frames can be taken at any temperature although I also take them at the same temperature as lights and darks. 

 

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23 minutes ago, TerryMcK said:

It is best to take bias frames at the same temperature as the lights. That what I used to do when using DSLR and it works well.

However most modern dedicated astro CMOS cameras don't need bias frames as just darks work well. Bias frames can give issues and are unnecessary.

Flat frames can be taken at any temperature although I also take them at the same temperature as lights and darks. 

 

Thanks for the clarification...I am also using a DSLR so I will try to take BIAS frames during the night.  I never get around to taking darks but BIAS seem more achievable especially if I'm dithering.

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You could take dark flats in that case instead of darks. Dark flats are the same duration as flats and can be used with bias frames.  That will minimise the time taken when taking calibration frames and give you more time capturing lights. 

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10 minutes ago, TerryMcK said:

You could take dark flats in that case instead of darks. Dark flats are the same duration as flats and can be used with bias frames.  That will minimise the time taken when taking calibration frames and give you more time capturing lights. 

Ok thanks, I haven't tried those before.  I will look into it👍

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16 minutes ago, PeterBolt said:

Ok thanks, I haven't tried those before.  I will look into it👍

If your camera is cooled, you can take dark frames during the day, along with your flats and dark flats. Once you have your master dark, (I stack 50 darks to make a master dark for each gain and exposure time I use), you can reuse your master dark for 6 months. You can also reuse your master flats many times over, unless your change anything in your setup, like rotating the camera.

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14 minutes ago, AstronomyUkraine said:

If your camera is cooled, you can take dark frames during the day, along with your flats and dark flats. Once you have your master dark, (I stack 50 darks to make a master dark for each gain and exposure time I use), you can reuse your master dark for 6 months. You can also reuse your master flats many times over, unless your change anything in your setup, like rotating the camera.

Unfortunately I only have a DSLR...

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37 minutes ago, AstronomyUkraine said:

That's the one big drawback of a DSLR, but you can still take darks outside on a cloudy night. I doubt the temperature changes will vary greatly for another month or so.

Well we certainly get plenty of cloudy nights 🤣 I think I will have more dark frames than anything else!

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1 hour ago, PeterBolt said:

Well we certainly get plenty of cloudy nights 🤣 I think I will have more dark frames than anything else!

You can always record the temperature you are taking them at, and build a huge dark frame library. 🤣

 

Check this out, might be worth investing in one of these.

 

https://astromart.com/classifieds/astromart-classifieds/ccd-cameras-astro/show/canonnikon-dslr-cooler-with-temp-controller

Edited by AstronomyUkraine
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1 hour ago, AstronomyUkraine said:

You can always record the temperature you are taking them at, and build a huge dark frame library. 🤣

 

Check this out, might be worth investing in one of these.

 

https://astromart.com/classifieds/astromart-classifieds/ccd-cameras-astro/show/canonnikon-dslr-cooler-with-temp-controller

I have a 1000D so no flip screen 🤔 I think I will wait and save up for a cooled camera.  Any recommendations.  My FL is 1000mm reduced to 900mm with my Coma Corrector.

 

Although the sensible side of my brain says I should probably upgrade my mount before getting a cooled camera.  I am currently using an AVX.

Edited by PeterBolt
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8 minutes ago, PeterBolt said:

I have a 1000D so no flip screen 🤔 I think I will wait and save up for a cooled camera.  Any recommendations.  My FL is 1000mm reduced to 900mm with my Coma Corrector.

 

Although the sensible side of my brain says I should probably upgrade my mount before getting a cooled camera.  I am currently using an AVX.

The mount is the most important item you can buy, but if your guiding is reasonable, a new camera will certainly improve imaging results. Then you have the choice of mono or OSC cooled cameras, and the added cost of a filter wheel to house mono filters, if you choose that option. As far as cameras go, many good brands are on the market. ZWO, Altair, QHY and many more. The camera would also depend on how deep your pockets are.

 

The resolution of your scope with a camera similar to my ZWO 1600, with a pixel size of 3.8, would give a resolution of 0.87, which is perfect, meaning no oversampling or undersampling. Check out various cameras with your scope, and enter the info on this site.

 

https://astronomy.tools/calculators/ccd_suitability

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50 minutes ago, AstronomyUkraine said:

The mount is the most important item you can buy, but if your guiding is reasonable, a new camera will certainly improve imaging results. Then you have the choice of mono or OSC cooled cameras, and the added cost of a filter wheel to house mono filters, if you choose that option. As far as cameras go, many good brands are on the market. ZWO, Altair, QHY and many more. The camera would also depend on how deep your pockets are.

 

The resolution of your scope with a camera similar to my ZWO 1600, with a pixel size of 3.8, would give a resolution of 0.87, which is perfect, meaning no oversampling or undersampling. Check out various cameras with your scope, and enter the info on this site.

 

https://astronomy.tools/calculators/ccd_suitability

I think I might try and get another winter under my belt using what I have before I buy anything else.

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16 minutes ago, TerryMcK said:

There might be a few mounts and other astro gear being unloaded over the next day or so in Felixstowe. The Evergreen ship that blocked the Suez Canal finally docked today.

Here in Europe ioptron and Skywatcher mounts are pretty thin on the ground. 10 Micron are ready available, if only I had the cash for one. 😀

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1 hour ago, MarkAR said:

There an AZ-EQ6 up for sale on SGL, looks hardly used.

 

I am interested but not sure what SGL is.... could you send me a link? Thanks

 

I've just worked it out... stargazers lounge!  I will take a look 👍

 

 

 

 

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