Snapshots with refurbished reflectors

[timh]

Here (Thames valley UK) conditions for imaging have been atrocious for a couple of months or so. I took the opportunity to get my SW PDS200 and OO (UK) VX12 (300 mm/ F4 ) Newtonians refurbished at Orion Optics.. recoating the mirrors of the former and re-aligning/ cleaning the optics of the latter.

It was like getting two new telescopes back - so obviously I wanted to get both fully tested and collimated. Having first tweaked the secondary mirror alignment using a laser (Hotech) and then a Cheshire eyepiece for the primary I was - in the end - with the help of Sharpcap livestacking - able to get some images back that showed both telescopes were set up and performing well despite such difficult skies.

The first PDS200 image of M81 was an SC 16 bit autostack comprising 15 x 40s (AS1294MC gain 124, 1.05 arcsec. pixel at F 4.5) taken within a 10 minute window under murkish moonlit skies on 01/05. It was further processed within PI

The second OO VX12 image of M106 was taken on 18/05 with a mono AS1294MM (0.4 arcsec/ pixel at F 4) under truly horrible conditions. It comprises a 16 bit autostack of 43 x 10s exposures livestacked over about 2h combining just the occasional cloud gap 10s frames that were both sufficiently bright and sharp with an FWHM < ~ 2.3. The drift over the course of 2h meant that only the lower right hand part of the full image was stacked (hence M106 is up at the top left edge).

I was pretty happy with these because although by no means great images they confirmed that both telescopes were well set up and working well (nice round stars which can be an achievement at F4). They also - I think - demonstrate that - especially with large telescopes - it is possible to see really quite a lot of image detail within short total exposure times and under poor conditions. The PDS200 image is 10 minutes and the average FWHM ~ 3. The VX12 image is only a total of 7 minutes and the FWHM is about 2.0. So EEA is quite possible even when serious imaging isn't.

Tim

[admin]

Hi Tim,

great report and it's good to hear that the refurbishment project has turned out well. I particularly like the M106 image - you can see a lot of detail lurking there that with a bit more exposure time would come out above the noise level.

cheers,

Robin

[turfpit]

Tim

Looks like the recoat project went well. M81 with the 200PDS has good detail for 10s exposures 30s or 60s would be interesting.

Dave

[Menno555]

Well, that's a good start for those two, Tim Can imagine that you are happy with it.

Menno

[timh]

Thanks for the kind comments everyone. Yes OO seems to have done a really good job on both so I am pleased. The PDS200 especially had got quite dull and now it's working a treat.

The main problem now of course is the lack of darkness and even in the clearish skies that we have had these last few nights the seeing has been poor (PDS2 guiding at 1.5 to 2 arcsec RMS). Nevertheless have managed to beat that to some extent by using short exposures.

Tim