Filter tests and an actual clear night (shock)

[wulfrun]

An amazing coincidence, totally at odds with the laws of the universe and telescopes. Yesterday postie dropped off a UHC filter to join the variable polariser I've had for a while but yet-unused. Looked out early evening and saw about 50% clouds, so no holding of breath. After dinner though - wow! Clear skies AND two filters to try, this can't be possible? Oh and a new Telrad too. The clear skies have come as a bit of a surprise so I have no set plan, I'll make it up as I go along and most things are new to me, in a scope, anyway!

I pulled the 150PL out of the shed and set up, despite the plumetting temperatures. Popped the unaligned Telrad on (base was already there) and aimed at the Moon, nope not in eyepiece - no surprise really - but I can tell it's not far away in the ES20mm. Manage to get the Moon centred and quickly adjust the Telrad fairly close so now I can actually use it. I don't have anything distant enough for daytime adjustment so I have to go the faffy route. Quick swing over to Rigel to see if it's good and yes, not too bad for now. Back to the Moon and jeez it's bright - filter test for the polariser then. Yep, well worth the money since I can dial it down nicely now. Spent some time wandering around the Moon, swapped out for the Hyperfelx and zoomed in for a good look around the terminator. Fascinating to see some peaks lit up brightly, just into the darkness beyond the terminator. This is my first lunar "exploration" so I'm very chuffed and suitably wowed! I can appreciate the "reach out and touch it" idea.

After this I decided to try out the UHC so I aimed at the Orion nebula (M42) with the ES20mm back in and noticed the Telrad's starting to mist up. Hmm, this will need a solution but wasn't unexpected based on reading. First view with no filter and the nebulosity is obvious but underwhelming, I can see all 4 of the Trapezium's stars, so on goes the UHC. Worth it? Oh yes! Ok, it makes the stars look a bit funny colour and the faintest of the Trapeziums has almost vanished but the improvement is noticeable and worth £20. I can also see some nebulosity around l-Ori (?), which is just near the upper edge of my FOV. I spent ages just oggling the nebula and getting damned cold! Just as I've read, the more you look the more you see - so sage advice there.

Finally decided that I'd spent enough time on M42 so I pointed up to the Pleiades, knowing I'm too high on magnification to see it in one go. Ah, the Telrad has become useless so that took some guesswork to find the right place. Just had a wander around generally in the area, gawping at just how many unknown-to-me stars there are around there.

Now I'm starting to get a bit too cold in the digits but I couldn't resist a go at Rigel. The Telrad by now having been returned to house-warmth, I found it by sighting along the OTA plus guesswork. Swapped in the Hyperflex and had a go - er no dice there I can't split it, it's either my technique/EP or the conditions. Worth a quick try but no box ticked.

My fingers are telling me to retire to the warmth of central heating so nothing else attempted. All in all, a lot of fun and now I need to find an un-powered Telrad anti-dew measure. I can see why so many folk rave over this finder but I don't want to hang a battery-powered solution off it if I can possibly avoid it.

 

Edited January 22, 2021 by wulfrun
I found the new edit!

[wibblefish]

Good times always good to get out especially with the new kit! Sounds like you got plenty in, I am still totally in awe of M42 and Pleiades especially since switching out my stock EP for some BST ones, surprised the difference it makes. The UHC sounds interesting will have to have a read up, I am yet to play much with filters, I have an ND polariser for the moon which has worked nicely and I have a yellow #8 to trial to see if it assists on bright objects to reduce the CA slightly. 

I am yet to have a proper lunar wander myself, sounds fascinating, I can only usually get at the moon when its full due to the angles of the garden / opposite houses and the few times I have managed its been to hazy for more than a couple of quick snaps on the camera phone so here is hoping for some clear skies at some point  

Ah Rigel, I am definitely going to keep trying to crack that one  

Interesting note on the Telrad dewing, I was debating getting a quikfinder to replace my annoying RDF (Telrad is probably toooo big) I suspect they have similar dewing issues but everyone does rave about both of those finders! 

[wulfrun]

51 minutes ago, wibblefish said:

Interesting note on the Telrad dewing, I was debating getting a quikfinder to replace my annoying RDF (Telrad is probably toooo big) I suspect they have similar dewing issues but everyone does rave about both of those finders! 

Yes, it took maybe a half-hour before it started being affected badly. To be fair it was sub-zero and everywhere's sodden. I have no personal experience of the Rigel but it's taller, so less sheltered and I'd expect it may be worse if anything. Fortunately the Telrad's footprint is academic on a 150PL but yes, they are BIG. The major improvement, apart from the obvious circles, is that you can actually turn the brightness right down to invisibility. The Celestron finder - with 2 circles - that came with the 150PL (fitted by PO) and the Virtuoso's RDF cannot be turned dim enough in my opinion. They just drown out fainter things even at minimum.

I have an idea for the Telrad - a springy clothes-peg with two rectangles of foam glued in between the arms - clip it over the screen when not in use, covering the screen both sides. Tie the peg on with string so it isn't lost. I'll post about it if I find a solution that works.

[Fraunhoffer]

Theres a simple DIY dew shield design here: Home Built Astronomy - Telrad Dew Shield

 

[wulfrun]

5 minutes ago, Fraunhoffer said:

Theres a simple DIY dew shield design here: Home Built Astronomy - Telrad Dew Shield

Thanks - I had thought of something along those lines anyway, then the clothes-peg idea popped into my head and seemed plausible too. Not tried either yet.

[John]

I use the Rigel and I've owned a couple of Telrads. The Rigel stays dew free a little longer in it's stock state and it's easy to make a simple dew cover for it from a small piece of cardboard. I had an add on dew shield / RA mirror attachment for the Telrads which was a bit of a fiddle but did work.

Last night was quite dewy though. Even my primary mirror got fogged up at the end of my session, and that practically never happens here. I had to keep the optical finder capped when not using it to keep the dew at bay on that.

I was playing with filters last night as well with my 12 inch dob, comparing filterless vs UHC vs O-III vs H-beta on Messier 42. Still think I prefer filterless on balance but it's interesting to see different portions of the nebula responding in different ways to the filters.