NGC 1857 / Herschel VII-33, an Open Cluster in Auriga - 24.03.2024

[josefk]

Another one from Sunday evening here. NGC 1857 is a "smallish" (10') Open Cluster in Auriga and an object on the Herschel 400 observing programme (Herschel VII-33).

I've observed it before this weekend at a low x70 in a 95mm refractor and made the notes "a meagre group of just 6 or 7 stars". I nearly made the same mistake again this Sunday when first viewing at x100 (130mm refractor) but thankfully the central star of the cluster (HD 34545) caught my eye this time for its lovely orange shade visible this evening and i popped in a shorter EP to achieve a closer look at x200, at this magnification the group was really quite rewarding. 

HD 34545 was a bit of a conundrum - its a multi star system but i couldn't see the notionally brighter components of it while seeing some of the fainter ones !?*?.

B at Mag. 13.05 (p17.4” & ⍬343º) is missing and while this could be explained by a lack of transparency on the night and my 130mm aperture, H which i could see is a nearly identical Mag. 13.08

C at Mag 11.10 (p28.2” & ⍬293º) is also missing (i may have caught this a couple of times with averted vision but not certainly) even while i could see F at Mag. 12.56 and G at Mag. 11.72 with direct vision 100% of the time (all values Stella Dopie).

Anyway, one to come back to for those components and lesson learned (again) to vary the magnification. NGC 1857 is definitely overshadowed by its big boy neighbours M37, M36 and M38 but that central orange sun is worth the time of a short detour! Recommended.

For what's its worth sketching this has been instrumental to determining after the fact what i could and couldn't see so while the aesthetic value is possibly a bit low the observation value for me is well worthwhile. 

[SwiMatt]

Interesting observation! And neat sketch, I really like the way you put down details on the page.

On Stellarium, the central star HD34545 is marked as a variable star, I wonder if part of the variability might be due to some of the components being variable? I couldn't find confirmation, but this would explain the absence of B and C.

[josefk]

Thanks @SwiMatt , per its variable nature - mmmh. Not sure and TBH i hadn't factored that in. I will dig into it the possible range now for my own curiosity. It isn't so bright and they are not so close i would expect glare to be playing a part but my curiosity is piqued 🙂 

[SwiMatt]

1 hour ago, josefk said:

Thanks @SwiMatt , per its variable nature - mmmh. Not sure and TBH i hadn't factored that in. I will dig into it the possible range now for my own curiosity. It isn't so bright and they are not so close i would expect glare to be playing a part but my curiosity is piqued 🙂 

Fair, glare might be another aspect of it. For curiosity, what is the separation between A and D or A and F?

[josefk]

From the horses mouth @SwiMatt:

[SwiMatt]

It is a very interesting "problem"  Thinking that I would like to track down NGC 1857 myself and report back!