An M63 in 1hr

[paul]

This is the result of just over an hour of LRGB out 3 hrs of so-so subs. Very hazy conditions and some weird tracking issues took the rest.  I tried for some Ha on the second night but chickened out with the forecast changing by the minute. This is 50% downsize.

 

Scope: 250mm OO, Camera ASI1600mm.

 

[paul]

With the bigger scope I seem to be clipping the brighter stars too easily, I need to think about halving the exposures and doubling up. Oh for a few extra bits😉.

[Bob-c]

A nice image Paul, the dust lanes stands out well.

 

Bob.

[AstronomyUkraine]

1 hour ago, paul said:

This is the result of just over an hour of LRGB out 3 hrs of so-so subs. Very hazy conditions and some weird tracking issues took the rest.  I tried for some Ha on the second night but chickened out with the forecast changing by the minute. This is 50% downsize.

 

Scope: 250mm OO, Camera ASI1600mm.

The image looks fine, with some great detail in the dust lanes. I don't know what your sky pollution is like, but I never take longer than 2 minute exposures with RGB and 1 minute with Lum with my 1600. I live in a Bortle 4 area, and shoot at gain of 75 and an offset of 15. My scope is a 120mm refractor. With that light bucket of yours, you can easily lower the exposures times.

[paul]

11 hours ago, AstronomyUkraine said:

The image looks fine, with some great detail in the dust lanes. I don't know what your sky pollution is like, but I never take longer than 2 minute exposures with RGB and 1 minute with Lum with my 1600. I live in a Bortle 4 area, and shoot at gain of 75 and an offset of 15. My scope is a 120mm refractor. With that light bucket of yours, you can easily lower the exposures times.

Thanks 🙂. It was  L:60s, RGB: 120s which has worked really well for the 150mm. (If I try narrow band its been 300s). I'm still new to the 1600 and haven't messed with the gain so default 139 and 50 offset. Its something I need to research - if it gives more dynamic range then I'm interested but otherwise it sounds like potentially making S/N worse. I heard that the offset is locked at 50 in the ZWO driver so had not even considered that. 

 

I think I'll try L:30, RGB: 60. I like to loop the sequence so I always have a set of LRGB but if the sub is too short that's a lot of filter switching and wasted time and I worry I'll age the filter wheel prematurely! So I'll probably try a sequence like LLL,RRR,GGG,BBB looped but that is more than a simple sequence.

[peter shah]

a great shot....pretty deep too

 

[AstronomyUkraine]

23 minutes ago, paul said:

Thanks 🙂. It was  L:60s, RGB: 120s which has worked really well for the 150mm. (If I try narrow band its been 300s). I'm still new to the 1600 and haven't messed with the gain so default 139 and 50 offset. Its something I need to research - if it gives more dynamic range then I'm interested but otherwise it sounds like potentially making S/N worse. I heard that the offset is locked at 50 in the ZWO driver so had not even considered that. 

The gain and offset are not locked in the 1600. ZWO for some reason changed unity gain from a gain of 139 and offset of 21, to a gain of 139 and an offset of 50. I have tried the new unity setting, but reverted back to the old settings. The default setting for high dynamic range is a gain of 0 and an offset of 50

 

You can make your own custom settings quite easily in the camera driver. As you see from the image below, I have two custom settings. To make a custom setting, just click the edit button, and fill in the respective rows with a name for your setting, followed by the gain and offset value.

 

My advice would be to experiment until you find a combination that works. I would definitely lower the gain for broadband imaging and choose unity gain for narrowband.

 

 

 

[MarkAR]

Lovely image Paul, nice detail.

[Carastro]

Pretty good result for only 1 hour.  Presume you had to throw all the others away.

 

Carole  

[Greg M]

Mighty fine for only one hour of data. I can only imagine how great it would have been with three hours had you not had tracking issues.

[paul]

19 hours ago, Carastro said:

Pretty good result for only 1 hour.  Presume you had to throw all the others away.

 

Carole  

I did a simple stack in PI and there was very good contrast but the stars were twice the size and very obviously tear drop shaped. The worst images came in the second half with a strange ghosting. I'm not sure that it was tracking and PHD2 looked good and it impacted all the frames to some extent, it may have been droplets of condensation on the CC which is now more closer to the secondary or some diffraction through a tree. Here is a sample (it was getting light then too). The diffraction spike tells me I didn't lose focus and the second night the issue wasn't there so its not likely to be collimation.

 

 

Edited May 16, 2021 by paul

[paul]

10 hours ago, Greg M said:

Mighty fine for only one hour of data. I can only imagine how great it would have been with three hours had you not had tracking issues.

I am happy with the results all things considered, I like to grumble 😉.  I worked hard to iron out my process so its annoying when there are things I don't yet understand getting in the way.

[AstronomyUkraine]

4 hours ago, paul said:

I did a simple stack in PI and there was very good contrast but the stars were twice the size and very obviously tear drop shaped. The worst images came in the second half with a strange ghosting. I'm not sure that it was tracking and PHD2 looked good and it impacted all the frames to some extent, it may have been droplets of condensation on the CC which is now more closer to the secondary or some diffraction through a tree. Here is a sample (it was getting light then too). The diffraction spike tells me I didn't lose focus and the second night the issue wasn't there so its not likely to be collimation.

 

 

That looks almost like an alignment issue. I have had similar myself when I have overlooked an image with star trails. Once the culprit was deleted then restacked, the alignment was perfect.

[paul]

On 5/16/2021 at 7:24 PM, AstronomyUkraine said:

That looks almost like an alignment issue. I have had similar myself when I have overlooked an image with star trails. Once the culprit was deleted then restacked, the alignment was perfect.

I would agree but its in every single frame after about 2hrs, that's puzzling. Its why I suspect condensation or some diffraction effect. I have seen a similar effect when the view passes through a tree branch. I'm considering making a dew heater for the CC that I can fit  on the inside of the scope to keep dew off the glass element. I have some resistance wire to experiment with.

[AstronomyUkraine]

1 hour ago, paul said:

I would agree but its in every single frame after about 2hrs, that's puzzling. Its why I suspect condensation or some diffraction effect. I have seen a similar effect when the view passes through a tree branch. I'm considering making a dew heater for the CC that I can fit  on the inside of the scope to keep dew off the glass element. I have some resistance wire to experiment with.

For less than £19 you can purchase a ready made solution from ZWO. It is called an anti dew heater, and fits ZWO cameras. I have one myself, they work fine.

 

https://www.rothervalleyoptics.co.uk/zwo-anti-dew-heater-strip-for-zwo-asi-cooled-cameras.html