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alan potts

Zwo 071 ordered

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I have ordered my new Zwo 071 from FLO and a transformer to power the cooling. Are there any tips a newish and not very bright (IT wise) guy can learn from you more experienced people. The question of the Gain, which I believe can be varied is one that I am bit worried about.

I have also order a ADM duel mount bar so I can put my 70mmED on the mount too. How do you stop the mount returning to the home position 90 degrees from where it normally would?

Alan

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Posted (edited)

I bought an ASI071 to use with my RedCat-51 but haven't used it yet apart from a few test images. It's a14 bit camera unlike the 12 bit ASI1600 etc and also has a higher full well of 48600 e- compared to 20000 e- for the 1600. So gain settings with the 071 have less 'critical' effect on your images compared to the 1600. I would just start with the default unity gain of 90 and offset 65. The manual seems to indicate 94 as unity gain but that's not much difference. I did a bias test and the offset of 65 does avoid black clipping at unity gain so all's well there.

You'll need an IR cut filter (standard Luminance UV/IR cut is fine) as all three bayer colour filters pass significant IR according to the transmission graph. I had to get a 2" one to fit the RedCat.

For 'standard' EQ mounts the home position is whatever position the scope is in when you turn it on so just point the scopes north as normal. The puck will be 90 degrees out from before but the scope doesn't know that. :smile: With Eqmod etc you can set another position as the home position if you wish (ie. the location the scope is assumed to be pointing at when you turn it on) but the scope just works out your initial goto from this assumed home position. Plate solving and syncing will then make this assumed position more accurate.

Alan

Edited by symmetal
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10 hours ago, symmetal said:

I bought an ASI071 to use with my RedCat-51 but haven't used it yet apart from a few test images. It's a14 bit camera unlike the 12 bit ASI1600 etc and also has a higher full well of 48600 e- compared to 20000 e- for the 1600. So gain settings with the 071 have less 'critical' effect on your images compared to the 1600. I would just start with the default unity gain of 90 and offset 65. The manual seems to indicate 94 as unity gain but that's not much difference. I did a bias test and the offset of 65 does avoid black clipping at unity gain so all's well there.

You'll need an IR cut filter (standard Luminance UV/IR cut is fine) as all three bayer colour filters pass significant IR according to the transmission graph. I had to get a 2" one to fit the RedCat.

For 'standard' EQ mounts the home position is whatever position the scope is in when you turn it on so just point the scopes north as normal. The puck will be 90 degrees out from before but the scope doesn't know that. :smile: With Eqmod etc you can set another position as the home position if you wish (ie. the location the scope is assumed to be pointing at when you turn it on) but the scope just works out your initial goto from this assumed home position. Plate solving and syncing will then make this assumed position more accurate.

Alan

Many thanks for that, I just hope they get the e-mail in time about the IR/UV filter as there isn't a chance of getting one here.

Alan

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21 hours ago, alan potts said:

The question of the Gain, which I believe can be varied is one that I am bit worried about.

Congratulations. Cloud cover included in the order? Re gain settings, I would start with unity gain and exposures of about 2-4 minutes. Keep the temperature moderate (-20 C). For narrow band (if you do this) , high gain (200 - 300) and maybe 300 s exposures. Then experiment from there. If for some reason guiding doesn't work, use high gain even for ordinary colour, and exposures 10 - 30 s. Just keep the total integration time constant. Cooled cmos works best with a large number of subs. 

Also astrobin is a good reference if you look for images taken with a similar setup. 

Have fun. 

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32 minutes ago, wimvb said:

Congratulations. Cloud cover included in the order? Re gain settings, I would start with unity gain and exposures of about 2-4 minutes. Keep the temperature moderate (-20 C). For narrow band (if you do this) , high gain (200 - 300) and maybe 300 s exposures. Then experiment from there. If for some reason guiding doesn't work, use high gain even for ordinary colour, and exposures 10 - 30 s. Just keep the total integration time constant. Cooled cmos works best with a large number of subs. 

Also astrobin is a good reference if you look for images taken with a similar setup. 

Have fun. 

The weather station has already joined in, yesterday it was showing rain and today as well, not been a cloud in the sky for 10 days.

Don't know about -20, it is 30 degrees here until midnight, will it battle that gap, I have noted what you say about exposure time, I normally stick to 3 mins on the Canon, for no real reason, as you say try a few things and see what comes up best.

Alan

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Posted (edited)

I bought an ASI071 about a year ago and I love it, so congratulations Alan! I cannot imagine you can get a better APS-C sized OSC camera.

I do use master darks with it, but so far my imaging train has been clean enough to avoid using flats, and bias is not necessary with these cameras. I read up on it initially and found that gain 200 was usually optimal, with offset 30 and I have mainly kept it at that (I am sure that there are some situations where this may not be optimal, depending on sky conditions and object). Then I made a series of master darks (25 or more frames) using that gain and offset and a few different exposure times (2, 3, 5 and 10 min). Regarding temperature I keep it at -15°C. Lower temperatures do not help much as can be seen from the T vs dark current curve. I attach a 7 hour example image with my Esprit 150 from spring this year (M100 & Co).

Skärmavbild 2019-08-14 kl. 21.24.25.png

20190406 M100 RGB2 PS29smallSign.jpg

Edited by gorann
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2 hours ago, gorann said:

Lower temperatures do not help much as can be seen from the T vs dark current curve. I attach a 7 hour example image with my Esprit 150 from spring this year (M100 & Co).

Skärmavbild 2019-08-14 kl. 21.24.25.png

 

That graph is a bit missleading. Dark current doubles every 6 - 7 degrees of temperature increase. This means that lowering the temperature does have an effect. Otoh, you don't want to run the cooler at 100 %, because you don't have any control then. I would run it at about 75% max. 

2 hours ago, gorann said:

I read up on it initially and found that gain 200 was usually optimal, with offset 30 and I have mainly kept it at that (I am sure that there are some situations where this may not be optimal, depending on sky conditions and object). Then I made a series of master darks (25 or more frames) using that gain and offset and a few different exposure times (2, 3, 5 and 10 min).

Well, that shows how wrong I can be. I looked at the product page of the 071 and compared to my 174. The gain curve for my 174 seems steeper than for the 071 and unity gain is at a higher gain setting. Unity gain for the ASI071 is at setting 90, while for mine it is at 189. Also dynamic range is a lot lower for my camera than the 071.

At 100 gain steps above unity, I could never use exposure times of minutes. 

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8 hours ago, gorann said:

I bought an ASI071 about a year ago and I love it, so congratulations Alan! I cannot imagine you can get a better APS-C sized OSC camera.

I do use master darks with it, but so far my imaging train has been clean enough to avoid using flats, and bias is not necessary with these cameras. I read up on it initially and found that gain 200 was usually optimal, with offset 30 and I have mainly kept it at that (I am sure that there are some situations where this may not be optimal, depending on sky conditions and object). Then I made a series of master darks (25 or more frames) using that gain and offset and a few different exposure times (2, 3, 5 and 10 min). Regarding temperature I keep it at -15°C. Lower temperatures do not help much as can be seen from the T vs dark current curve. I attach a 7 hour example image with my Esprit 150 from spring this year (M100 & Co).

Skärmavbild 2019-08-14 kl. 21.24.25.png

20190406 M100 RGB2 PS29smallSign.jpg

A lovely image there I must say. Can't say I understand a great deal of what is being said, maybe things will be a bit clearer when I get the camera and can see it working. At the moment Gorann I use dither, can that still be used with this type of camera, as I have to say I feel it works well with a DSLR.

Alan

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As others have said I would advise keeping exposures to several minutes. I tried 30s exposures with my asi1600 and found the time between exposures for image download and dithering cut into my overall imaging time too much. With exposures of several minutes there is no issue.

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