markse68

1 hour ago, NGC 1502 said:

 

If you live in London then you may like to go along to Baker Street Astronomers who meet in Regents Park.

 

Thanks Ed, I’ve got Flamsteed as my local society but they don’t meet for night time obs  till a bit later in the year- maybe next month actually 🤔 and I’ll definitely be going along to their public meets 

Yes indeed Raph- I looked at the double double last night as well 😊 I’m more confident I’m splitting them there as they split in different directions so it’s clearer- I have a bit of an issue with astigmatism at high powers on bright stars that makes them all look like doubles 😳 but I’m hoping to remedy that soon 🤞

It’s funny- once I found it I could then just about make out the stars of the  “square” of Hercules but only with the perspective of knowing where m13 is 😂 The trouble with the phone apps is without that perspective I don’t get a feeling of scale at all a lot of the time when the key stars are so dim. 

Thanks Mike- I’ll look to that site for the next one- looks very useful. I determined at the start I didn’t want goto as I wanted to learn the Sky so I guess I’m stuck doing it the hard way 😉 

Rob that is pretty profound isn’t it! I like thinking about things like that. It’s pretty amazing that I could cry for help from the middle of Plumstead common on a Tuesday evening  and receive support real-time from folks who actually could offer that help as well! 😊

Clouds rolling in  from the west- just enough time to have another go at Pi Aquilae ( still not convinced I’m splitting it). And a few minutes on my new favourite the double cluster- real sense of textured clouds of star dust even from here in se London! Beautiful 😊 Time to pack up now. 

Thanks to all I have found it! Not what I was expecting at all and pure luck I think that I stumbled on it but yes a very faint fuzzy from here in Plumstead- less defined than the ring but with averted vision I can make out it is thousands of tiny faint stars. If they were a bit brighter they’d be mesmerising I’m sure. Anyway- well chuffed and thanks again 😊

Thanks Sunshine, I thought it was meant to be naked eye visible but yes it is a bit like looking for a needle in a haystack blindfolded 😞 I have managed to find the ring nebula but that part of the sky isn’t as badly affected by the lp being closer to zenith. Would you say it’s dimmer than the ring neb?

Third night in a row and I just can’t find the Hercules cluster and it’s driving me nuts. Trouble is the lp is so bad I can’t make out Hercules constellation at all. But I can see Vega and Arcturus and according to sky safari it should be almost on a line between them a bit closer than half way from Vega. Scan as I might it’s not there though! What should I be looking for- does it need power to see it as a cluster? Would it just look like a star through a 40mm ep (40x mag)?

Please help me find it 😊 Thanks!

3 hours ago, iPeace said:

Nice one, I've turned it into an observing list to try soon.

That’s what I keep doing- the list is growing exponentially 😂 But I am finding some and in the process starting to learn the Sky- this forum is doing a great job there 👍

Going for a major overhaul- replacing secondary and fitting 2" focuser. It'll take a bit of time as I'm going to make a new secondary holder but I just ordered a protostar mirror (toss up between Protostar and Antares but Bryan answered email immediately and yet to hear from Antares a week later so...) so I'm commited now

Reason for replacing secondary is my current one is 1.75" and is positioned so the focal plane is a whopping 120mm from the tube. That's a 20% diameter obstruction so not bad but I figured if I went for 1.52" I could move the focuser up 25mm and shorten its protrusion correspondingly, plus a lower 18% obstruction won't hurt given it's quite long f7.3. Also I have a bit of annoying astigmatism at high power. Inconclusive testing with optical flat for fear of damaging the coating but rotating the primary didn't seem to rotate the astigmatism so I'm hoping a new sparkling high precision mirror will improve matters. Plus old secondary should really be re-coated anyway as it looks pretty poor surface finish under microscope so may as well replace it.

Modelled the scope up in solidworks and I'm fairly confident it's fairly accurate now after much measuring

I picked up a great deal on a moonlite focuser but its meant for an SCT so has a very short focus travel and a longer tube for it was 50$ postage alone (!!) so I've calculated its position to allow most of my current eps to focus though some will likely need rings making or pulling out a bit- no big deal really. I don't think Ron at Moonlite was very impressed with the plan though... It's a bit daft really but too much of a bargain so I'll make it work. The focuser base will be 3d printed in nylon

Haha- just checked on that site and it says Bortle 8 for my site- that's bad isn't it? The other night I could see Vega but couldn't make out the stars of Hercules and no luck finding M13 despite clear dark sky

I couldn't see it the other night with 8.5" despite clearest skies since I bought it but then I only have a sky glow filter and SE London skies are about as bad as they get I think? Maybe with an oiii which I need to get I think...

Looking forward to your findings as this is a neat sounding system if it works reasonably accurately. Is there something similar for iOS?

Might be seeing condition related but high power on the planets doesn’t really work for me here. I’m finding on my 1625mm fl most pleasing views with a straight 15 or 18mm ep. 10 is ok but 5 (4.8) is an ill-defined mush. 5 on doubles last night seemed to work much better though with the clearer skies, and on moon was still quite pleasing

Me three- though for only 3 hrs 😉 Nice to think of us all out there separately looking up- connected in some way. Seeing is getting better and better- last night was the best session yet- found loads of new things including first look at Uranus!  Gave up a bit frustrated not finding Hercules cluster but I couldn’t really make out the constellation so was just swinging the scope around in vain not really knowing what I was looking for. 

Sometimes it’s tempting after a few nights of clearish skies to think I’ll not bother- just more of the same, but persistence definitely paid off last night for me 😊

Past couple of nights the seeing has been much better hasn’t it- really sharp views of the gas giants despite haze and high altitude blanket. I really enjoyed Saturn too last night 😊 (and Jupiter with GRS) 

Looks like it doesn’t it- it’s really an optical flat 😃- to check my secondary. I’m unnaturally happy about this... combination of nice tools and new hobby I guess 😉

this just arrived and it excites me way too much - a tub of Russian shaving cream!😳😉

Probably a consequence of @FLO price increases?

Well it seems improved but still there 😞 Artificial star is a light on a distant crane (a bit windy this evening!)

I will try that next for sure but I think it will throw collimation too as the rim of the mirror isn’t perfectly parallel to the bottom surface. I actually taped it to prevent it rotating in case that happens 

Hi Paul, no I don’t know that it’s not the primary but I’ll cry if it is. The secondary mount just seems to be the most likely culprit

@Peter Drew I was told it was a Hysom primary but have no way of being certain- hope it is though. It’s not the best primary cell design by modern standard but I have freed up the mirror- removing the felt pads that jammed it in around its periphery and the 3 cork pads that supported its base. I replaced them with ptfe tape and the mirror can now slide around fairly freely in all dimensions.

This is today’s bodge to hopefully see if it is the secondary mounting causing the issue. I removed the larger pads of UHB tape I’d previously used and instead used 4 small pads of pe foamed tape whose height equals its width. This makes them quite wobbly and should hopefully decouple the mirror from any bending of the support plate and it’s thermal movement. Not trusting the small area of double sided bonding I’ve reinforced it with thin strips of self adhesive aluminium tape doubled up. This should still allow the mirror some movement but hopefully stop it dropping on the primary! Fingers crossed .

I think I will invest in a new mirror as this one doesn’t look great under a microscope. It has scratches and small chips in the glass and the backside actually seems better polished than the silvered side, though that might just be the coating.

Oh in case the primary does have a rolled edge (not sure that would cause such astigmatism though?) I made up a mask that shaves 3mm off the outside edge, still leaving 8.5” clear aperture as the mirror is closer to 8.75” actually. 

I’ve had an issue with astigmatism with my scope since I got it and tried a few things but haven’t cured it yet. It shows as stars under high magnification blurring out linearly then perpendicular to that when racking focus back and forth. It’s making splitting doubles very hard and I feel the scope is capable of better.I think my collimation is ok and the primary is meant to be a Jim Hysom  who apparently didn’t make bad mirrors.

 My suspicion is it’s caused by the secondary and more specifically the mount. I liked the mount at first- it separates tilt from rotate and height so nice and straight forward to dial in. But it’s design is I think flawed, inevitably imparting a bending moment on the mirror- especially the way the mirror is mounted to it with double sided foam tape. Differential thermal expansion could also be adding to it. I tried to remedy this by sticking it just at 2 places rather than over whole surface but it made no difference- possibly worsened it. The problem is to adjust the angle and lock it in place you must apply some torque to the 2 adjusting screws, pulling the mount and mirror against the fulcrum bar- not good.

i like the look of the AstroSystems mounts- I think the way they support the mirror around it’s edge is probably ideal with no forces on the mirror other than gravity. So I may order one but am also toying with making my own mount- can’t be that hard can it? 🤔

Ive ordered a Russian optical flat to check the secondary flatness but it hasn’t arrived yet and I can’t wait...

I might look to get a smaller secondary as I think this one’s a bit big (44mm) for an 8.5” f7.5 scope? Certainly the focal plane is quite a long 120mm out from the tube wall which seems a bit unnecessary- a smaller mirror further up the tube might be better. Need to play with the numbers in Newt.

in the mean time I’m going to try another mirror mounting  bodge with this mount to see if that helps and my theory is right...

There’s definitely something not right I think- have some ideas just need to experiment a bit

It’s amazing how addictive splitting double stars can be isn’t it? Never would have believed it! Thanks for adding another couple to my list of challenges Stu- it’s getting quite long now and without too much success so far. I’m struggling to optimise my scope- still suffering astigmatism which is killing high power star views 😞 But it’s ok- it’s actually a fun if frustrating  part of the journey I think- cracking the scope mechanics to improve the view. I think it’s the secondary mount bending the mirror slightly- a flawed design and I’m umming  and ahhing about  whether to try to improve it or just replace it. Spent a few hours this week when weather permitted on Pi Aqu without success (I think I’m looking at the right star now 😉) and only managed one of the double double 😞 I think my 8.5” f7.5 should be doing better than this but seeing hasn’t been great either. Didn’t manage Antares yet either and unfortunately it’s getting too low too early now so will have to wait