Pleiades M45

[JR]

I wasn't going to bother last night but clearing skies got me outside, if only for about an hour of imaging after setting up. Reappearing cloud stopped play. All a bit blurry and I wonder if the lens was misting. The strange diffraction spikes may be a clue. I checked at the start of the imaging run but I can't have been vigilant enough. Even so it's good to be getting any result with the unhelpful weather.

I used the first 40 out of a total of 136 20 second exposures, taken during the clearest interval, at gain 100 with the ZWO asi533 MC Pro one shot colour camera, Esprit 80ed f5/400mm. 40 darks, DSS and Pixinsight.

James

[JR]

Finally discovered how to get something in Pixinsight to work so Mk 2

[trevsie7]

Very nice James. I find M45 quite difficult to get the nebula to come out well without over exposing the stars.

On Sun, 7 Mar 2021, 20:45 'JR' via croydonastro, <croydo...@googlegroups.com> wrote:

Finally discovered how to get something in Pixinsight to work so Mk 2

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[tcos...@gmail.com]

Hi James, like Trev I find the Pleiades really quite difficult to image, but you have captured both the stars and the wispy nebulosity which the stars happen to be passing through really well. Strange how the weather works out, because the night you imaged this target through gaps in the cloud, I had a really clear night right until just after midnight. Managed to get 3+ hours in on Markarian's Chain (thanks for the suggestion Trev). Re the star spikes you are probably right about dew on the objective lens. Do you use a dew heater? If you can use one then you should, especially when imaging in the winter months. Also, is there a way of increasing colour saturation in your image? I accept that you had to discard a lot of sub exposures, but if there is a way to increase the blue colour saturation in the data you have, it would make a difference to the end result.
Kind regards
Tim C

[JR]

Thanks Tim. Very good points.

I do have a dew heater but have rarely had a problem with the refractor as it has an ample dew shield. I should have checked. It was very cold and the scope was outside for some time cooling down and must have been at ambient minus something.

On the blue, easier said than done, by me anyway!

regards

James

Sent from my iPad

> On 8 Mar 2021, at 21:01, tcos...@gmail.com wrote:
>
> Hi James, like Trev I find the Pleiades really quite difficult to image, but you have captured both the stars and the wispy nebulosity which the stars happen to be passing through really well. Strange how the weather works out, because the night you imaged this target through gaps in the cloud, I had a really clear night right until just after midnight. Managed to get 3+ hours in on Markarian's Chain (thanks for the suggestion Trev). Re the star spikes you are probably right about dew on the objective lens. Do you use a dew heater? If you can use one then you should, especially when imaging in the winter months. Also, is there a way of increasing colour saturation in your image? I accept that you had to discard a lot of sub exposures, but if there is a way to increase the blue colour saturation in the data you have, it would make a difference to the end result.

> To view this discussion on the web visit https://groups.google.com/d/msgid/croydonastro/1734d01d7145e%24382d1940%24a8874bc0%24%40gmail.com.

[JR]

Actually just had a thought. ZWO cooled cameras are meant to be susceptible to dew on the chip cover glass and there is a heating kit they make to prevent it. Must investigate further

Sent from my iPad

> On 8 Mar 2021, at 22:10, JR <drja...@aol.com> wrote:
>
> Thanks Tim. Very good points.

[trevsie7]

I have never had a problem with condensation on my ZWO sensors. I think it usually occurs if you don't warm it up slowly after an imaging session. SGPro has a warm up function that is run before you disconnect the camera. Taking it indoors cold would probably cause condensation.   I do though use a heater just behind the dew shield on my Esprit 80mm and no longer have problems with dew on the objective lens.

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[JR]

Interesting.  Thanks for the info Trevor.

It's not the warm up phase that's the problem for me.  I do step cooling both down to target and for warming to avoid thermal shock to the sensor, rather than condensation.  

Some of the ZWO cameras have built in heaters for the sensor cover glass, but mainly the earlier models where sealing wasn't so airtight.  The heat extracted by the TEC warms the camera casing according to ZWO, but there are still some reports of dewing on 1600s.  

Using my dew heater may do it but I am going to investigate the sensor as well.  Too few imaging opportunities make it a worthwhile precaution.  Remote telescopes may eventually be the only answer to clouds and LP.   I hope not.

James

Sent from my iPad

On 8 Mar 2021, at 23:10, trevsie7 <trevs...@gmail.com> wrote:



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