8 replies to this topic

[Rustler46]

After 4 beautifully clear nights where I didn't feel up to observing due to Covid, tonight I'll be having a go at seeing the supernova with my 10-inch push-to Dob. As if M101 isn't difficult enough under my Bortle 5 skies, the Moon is a big fat gibbous phase.

 

So that this inquiry didn't get lost in the many posts on the main M101 SN thread, I have a question. No doubt that I'll be able to find M101 with my DSC-Nexus-SkySafari rig, but discerning spiral arms will next to impossible. So the question:

• Would the use of a light-pollution rejection filter be of any use? I have two:
  • Thousand Oaks Oxygen-III
  • DGM Optics NPB Nebula
• No doubt either filter would make M101 itself essentially disappear. But might the supernova benefit from such a filter. I'll give it a try, perhaps just hand holding the filter in front of the eyepiece to see if the view changes with & without filter. Any advice you can offer would be appreciated.

Best Regards,

Russ

[Another_Dave]

So, my level of experience and knowledge pales in comparison to some of the others on here, but I have some modest experience with UHC and CLS filters and think I understand the basic physics.

 

The general idea with filters is to exclude unwanted light to gain contrast on sources where the desired light is concentrated in selected bands. Emission nebulae being the most obvious choice. Here, we can let some combination of light from excited Oxygen, Hydrogen, Sulphur atoms through and try to knock out some light from other broad-band sources like the moon, anthropomorphic light pollution, stars, galaxies. The emission nebula emissions are attenuated very little, the unwanted sources attenuated noticeably more - hence improved contrast at the expense of some brightness.

 

In your case, M101 and the supernova are both broadband sources. And will both be equally attenuated by the filters (give or take). Thus you will end up with a dimmer image and no useful contrast increase.

 

I think I have that right ...

[Bean614]

Don't use filters! And, you Don't need to see M101 to find the Supernova!  Just push your Dob to NGC5461.  It's right there, can't miss it! I've done this with a 10" Intelliscope Dob, and a 4" Refractor.  Easy pickens!

[Rustler46]

Thanks for the info, Dave and Bean. I'll give it a try tonight. Another marker in time for us astronomers.

 

Russ

[Redbetter]

Yes, the star hop is the key, identifying what stars you can see (and figuring out where the interloper is.)  A filter would alter their relative brightnesses, making the identification more difficult.  

[Rustler46]

Yes, the star hop is the key, identifying what stars you can see (and figuring out where the interloper is.)  A filter would alter their relative brightnesses, making the identification more difficult.  

Yes, that's exactly what I did. And I was able to identify nearby star patterns and convince myself I was seeing the SN. Nothing spectacular visually. But just being aware of what is going on physically makes it awesome, nonetheless.

 

This one reminds me a bit of the supernova in M81 in 1993. At that time I lived in Happy Camp, California with perhaps Bortle 3-4 skies. The galaxy's spiral arms were visible with the SN superimposed. My observing note for SN 1993J:

• 1993-April-11, Celestron-8, clear, no Moon, good seeing
• Supernova in M81 easily visible S. of M81's nucleus; ~mag. 11 (brighter than 11.9); stars of mag. 12.7 & 13.0 easily seen without averted vision; suspect reddish color of supernova; used chart from AAVSO Alert #169

Best Regards,

Russ

[Redbetter]

This one is not going to fade quickly, so you will be able to see it better in a week or two within the structure of the galaxy, with the Moon out of the way.  I put it a 11.2 V mag tonight.  It shouldn't fade more than a couple of tenths over the next two weeks.

[Ihtegla Sar]

Nothing spectacular visually. But just being aware of what is going on physically makes it awesome, nonetheless.

That was my assessment when I saw it the first time in my 5.5" under 18.5 MPSAS skies that were too bright to see M101. Star hopping to the SN and identifying it solely by reference to star patterns in Interstellarum and posted photos, it looked like just another dim star, barely visible in direct vision and there were brighter stars in the field of view that I needed to see to positively identify it (the SN makes a triangle pattern with two stars bright enough to be shown in Interstellarum). Nothing spectacular visually but awesome to know what I was seeing.

However, when I made it out to a dark sky (MPSAS 21.55, with no moon), and viewed it in my 20", the view of the SN in the context of M101 was nothing less than spectacular.

At 260x with a .46 degree field of view, M101 was big and bright, with many HA areas easily visible, and the SN, located very near a visible HA area in one of the spiral arms, was by far the brightest star in the field of view, shining like a beacon across the immense void of intergalactic space.

Edited by Ihtegla Sar, 01 June 2023 - 09:50 AM.

[ButterFly]

After 4 beautifully clear nights where I didn't feel up to observing due to Covid, tonight I'll be having a go at seeing the supernova with my 10-inch push-to Dob. As if M101 isn't difficult enough under my Bortle 5 skies, the Moon is a big fat gibbous phase.

 

So that this inquiry didn't get lost in the many posts on the main M101 SN thread, I have a question. No doubt that I'll be able to find M101 with my DSC-Nexus-SkySafari rig, but discerning spiral arms will next to impossible. So the question:

• Would the use of a light-pollution rejection filter be of any use? I have two:
  • Thousand Oaks Oxygen-III
  • DGM Optics NPB Nebula
• No doubt either filter would make M101 itself essentially disappear. But might the supernova benefit from such a filter. I'll give it a try, perhaps just hand holding the filter in front of the eyepiece to see if the view changes with & without filter. Any advice you can offer would be appreciated.

Best Regards,

Russ

The SN is very much a point source in our optics.  The galaxy and the sky background are extended objects.  Point sources don't dim with magnification, whereas extended objects do.  Give it higher power, unfiltered, in any given scope.  That will improve the SN's contrast against the galaxy and the sky background.

 

Extended objects also all have the same surface brightness at any given exit pupil, in any scope.  Point sources brighten with increasing aperture.  Another way to increase the contrast between a point source and the sky background (and the galaxy in this case) is to use larger aperture, if any are available.

 

If you use a filter, you dim both the point source and the extended object in the bands the filter rejects.  The SN is broadband so a filter would hurt it as much as the background.  A tiny planetary that looks like a point source in our scopes, on the other hand, wouldn't dim too much with an OIII filter, whereas the background would.  Both higher power and an OIII filter helps for planetaries.