Urban M101, in about an hour

[PortableAstronomer]

Hi everyone,

Well finally got some clear skies last night so I though I would have a go testing the Telescope Service off-axis-guider with the Skywatcher 190MN mak-newt.

I got fed up with autoguiding with a separate guidescope because of the annoying fixed mount on the Equinox 80 which would be the guidescope. Plus the need for extra dew heaters etc.

Good news is there's plenty of back focus available so I could put a filter drawer/ filter wheel behind the OAG.

Pictures:

1- The light pollution caused by nearby industrial-scale greenhouses, so we can export lots of vegetables.

It looks like a red sunset. It isn't !

2- Stack of 12x5 mins (60 min total) of M101, the unprocessed stack showing the light pollution

3- then after about 5 mins of basic processing using PixInsight.

You'll notice the background still isn't cleaned up, it's partly because the background extraction had to remove severe light pollution. But not a bad turnaround for 1 hour outdoors.

Details:

Equinox 190MN scope

EQ6 + EQMOD

TS 9mm ultra low-profile OAG

QHY5 autoguider

Stacked using DeepSkyStacker

PixInsight: Dynamic Background Extraction, Histogram stretch, noise reduction, saturation boost, further background extraction, then another slight histogram stretch.

[PortableAstronomer]

I'll be posting a review of the TS OAG unit with the 190MN scope soon; from first tests the guide stars are nice and sharp, not too difficult to find a guide star (for OAG standards), but the way the TS OAG is put together is a bit poor considering the price. The QHY5 as an OAG autoguider is not ideal because of the noise, but it's do-able most of the time.

There's an ugly dark top-left corner on this photo of M101. I don't think it's the shadow of the OAG prism because it was not in the corner of the CCD chip (it was above the long edge). I calibrated using 30 flats (as well as the bias frames of course), and used Dynamic Background Extraction in PixInsight but it still left a rather ugly gradient towards that corner. I find that the old PixInsight LE (that used to be free) did this sort of gradient removal much better.

[harry page]

Hi

The new dbe has a much lower tolerance setting by default ! than the old dbe

If you are having a problem try increasing the tolerance from 0.5 to 1

Harry

[hunterknox]

This guy is very good indeed. Sir, I doth my cap!

[harry page]

Hi again

I also recomend background neutralization with images with a lot of background colour before dbe , gives dbe less to do

Harry

[MartinB]

You've worked wonders through the murk. I'm sure the background will succumb to processing eventually.

[PortableAstronomer]

Thanks Harry, will try that tip next time I get a spare hour from the missus !

[Demonperformer]

I am seriously impressed with the result under that level of LP - and with only 60 mins.

And I thought my mere streetlights were bad.

[myk68]

Really nice image and from more LP than I have, thats really good.

I'm still getting to grips with the processing side and of course getting guide to work, so I can only do 60-80secs each pic. Heres getting as good as this.

My cap is also dothed