IFN south of rho UMa in Ursa Major

[gorann]

I continue my hunt for Integrated Flux Nebulosity (IFN) with the RASA. The big yellow star to the left in the image is rho UMa and south is to the right in the image (which made for better framing). The big yellow and blue stars in the lower left quadrant are sig01 UMa and Sig02 UMa, respectively. My obsy is in a rural area and SQM this night showed 21.4, so quite dark. That helps a lot when hunting for IFN. The 8" F/2 scope also helps. That combination allows for detecting quite a lot of colour in the IFN.

I have not seen any images of IFN this area this close up, but there are some wider field images by Nawratil and others that I use to orient myself in my hunt.

I also post an annotated image (done in PI) revealing a lot of small galaxies from the PGC catalogue.

Collected 4 March with a RASA8 and ASI2600MC without filter. 51 x 5 min at gain 100, so 4.25 hours.

 

Edited April 5, 2021 by gorann

[carastro]

Wow

[almcl]

Fabulous images as always, Gorann.  I do like your quest for the IFN, way beyond anything I could achieve.

A question about settings on the ASI 2600, if I may?  What offset are you using?  I have had some difficulty with calibration recently and wonder what setting others are having success with? 

[carastro]

Bortle 2, I don't think I ever seen Bortle 2 skies, must be wonderful.

Carole 

[gorann]

35 minutes ago, almcl said:

Fabulous images as always, Gorann.  I do like your quest for the IFN, way beyond anything I could achieve.

A question about settings on the ASI 2600, if I may?  What offset are you using?  I have had some difficulty with calibration recently and wonder what setting others are having success with? 

Thanks a lot!

I always use gain 100, offset 30. Gain 100 is as you know the sweet spot with the sudden fall in read noise and maintained dynamic range. The offset 30 is just something that seems to work well. Temperature is set to -15°C.

[gorann]

11 minutes ago, carastro said:

Bortle 2, I don't think I ever seen Bortle 2 skies, must be wonderful.

Carole 

Hi Carole! Yes, I also thought I had seen tables saying my SQM readings (usually between 21.3 and 21.6) was Bortle 2-3. I am on the coutryside with no major city close by so no clearly brighter horizon. But now I see a table in Wikipedia (https://en.wikipedia.org/wiki/Bortle_scale) saying it would be Bortle 4-5. I hope Wikipedia is wrong for once. How do you translate SQM readings?

Edited April 5, 2021 by gorann

[carastro]

I usually use a LP map Like this, find your location and click on it and it will give you your Bortle scale.

https://www.lightpollutionmap.info/#zoom=4.00&lat=50.5529&lon=11.1192&layers=B0FFFFFFTFFFFFFFFFF

But have just done a google and found this:

https://www.cleardarksky.com/lp/ChrSprPkPAlp.html

Your SQM readings look like Bortle 4 according to that.

Carole 

[DaveS]

According to CO I have 21.66 and it says Bortle 4, edging towards 3. down the road in West Bexington it reckons 21.72 and just over the line into Bortle 3. Probably about right according to description on cleardarksky.com

[gorann]

8 minutes ago, DaveS said:

According to CO I have 21.66 and it says Bortle 4, edging towards 3. down the road in West Bexington it reckons 21.72 and just over the line into Bortle 3. Probably about right according to description on cleardarksky.com

This is an example of the Bortle scale I have seen before. Here the SQM values are much less compressed at the top than the "new" one in Wikipedia, and gives me Bortle 2-3.

Source: https://www.researchgate.net/figure/Levels-of-the-Bortles-dark-skies-scale-with-the-corresponding-sky-brightness-magnitude_fig1_337547281

[DaveS]

That would put me in the middle of Bortle 2, however, from the appearance of clouds (Low cloud is a dark hole, high cloud picks up the LP from Bridport and Weymouth) and the Milky Way (Bright and detailed at the zenith with structure down to the horizon), I would say it agrees with the cleardarkssky.com description, of the dark end of Bortle 4. Ophiuchus is far too low to show much of anything, let alone a bulge.

In any case, in comparison to Ruislip where I moved from, it has been a revelation.

I need a SQM.

[gorann]

4 minutes ago, DaveS said:

That would put me in the middle of Bortle 2, however, from the appearance of clouds (Low cloud is a dark hole, high cloud picks up the LP from Bridport and Weymouth) and the Milky Way (Bright and detailed at the zenith with structure down to the horizon), I would say it agrees with the cleardarkssky.com description, of the dark end of Bortle 4. Ophiuchus is far too low to show much of anything, let alone a bulge.

In any case, in comparison to Ruislip where I moved from, it has been a revelation.

I need a SQM.

My problem with the subjective description of sky darkness of the Bortle sky scale is that it all depends on the observer. My soon 62 year old eyes are clearly not as light sensitive as they used to be, so I need the SQM to tell me how dark it is on a particular night.

[david_taurus83]

The Light Pollution Map info is about 6 years old now so things have probably gotten worse or, hopefully, better with the recent initiatives with LED streetlights. Though I seen a report a few months ago that suggests only 20% of light pollution comes from streetlights. 

https://www.darksky.org/tucson-street-light-experiment/

 

@gorann great image of the IFN btw!

[The Admiral]

On 05/04/2021 at 11:18, gorann said:

The big yellow star to the left in the image is rho UMa and south is to the right in the image (which made for better framing). The big yellow and blue stars in the lower left quadrant are sig01 UMa and Sig02 UMa, respectively.

What caught my eye was how tiny the bright stars appear in this image. Or am I imagining it?

A lovely image as usual Göran.

Ian

[gorann]

1 hour ago, The Admiral said:

What caught my eye was how tiny the bright stars appear in this image. Or am I imagining it?

A lovely image as usual Göran.

Ian

Thanks Ian! The trick is many small curved stretches of the faint stuff in the data with a careful look at avoiding stretching the bright stars too much.