Pixies

Yes - I really enjoy observing M92. It's much smaller and dimmer than M13, but I think I prefer it. It lacks the 'wow' factor of huge M13, it's more subtle and less dense. M37 is an interesting target. It's an open cluster, but more 'globular' looking than most. I only saw it for the first time, last month, but now it's a regular fave.

Yep - as John implies, it all depends on the exit pupil. As magnification increases, the bright objects and the dark sky both get darker - but the sky appears to darken more initially. There is a trade-off between the brightness of the object and the brightness of the sky. The sweet spot varies. Some say a 2mm exit pupil offers the best contrast. There have been quite some arguments over this on Cloudy Nights! Personally, I find a 2mm exit pupil great. Exit pupil = Eyepiece focal-length / focal-ratio of scope. So with my F/6 dob, a 12mm eyepiece gives a 2mm exit pupil. So your 52º_30mm and 68º_24 EPs have the same TFOV, but the latter will have darker sky and better contrast between sky and stars. If your scope was F/6, the former eyepiece will have an exit pupil of 5mm, and the latter will have a 4mm one. Also - and this could well not apply to you, smaller exit pupils are easier for your eye to handle if it suffers from any aberrations, like astigmatism. I know there are some SGL members who can use the more powerful EPs without their specs, but once the exit pupil hits a certain size, they need their glasses to observe.

The whole point of a Cheshire is that you don't need to see the primary clips. That's only when you are using a collimation cap. With the Cheshire, once you have used it as a sight-tube to position the secondary under the focuser, you then adjust the secondary tilt so that the doughnut is directly under the crosshairs. Having the doughnut and crosshairs aligned means the primary is centred in the secondary. You don't need to worry about the primary mirror clips.

Beware black-painted bolts. The paint can strip off, if you're not careful, and you'll be chasing it all around the cell. Try and get black stainless steel. If you want to use threadlock when you put them back, use Loctite blue so they can be removed in the future.

I'd give him a shout and se what he suggests. He might have come across something like this before. Could be worth asking him if he knows of any similar scopes that might be loaned out?

measure up the unbroken bolts and get new ones here: https://www.accu.co.uk/en/64-low-head-cap-screws#elasticsearch_id_feature_955463=955463_473&id_elasticsearch_category=64&orderby=ranking&orderway=asc I'm assuming they have been held in with something like Loctite Red. Can you get localised heat to the stuck bolts - with a soldering iron, say? Heat 'em up then try removing them with a big pair of pliers?

Get some chickens and a cockerel. He'll soon have the lights off.

Hi, The 114 AZ is a Bird-Jones design, with a focal length (1000mm) longer than the actual tube itself. This is achieved by using a spherical (not parabolic) mirror and an associated correcting lens placed in the focuser. This means that the collimation process is much harder - but correspondingly, precise collimation is not as essential with a spherical mirror. However, as it effectively already has a barlow lens installed, I'd avoid investing in a new one (or using the one supplied). I agree with @jonathan's suggestion of BST Starguiders or Celestron/SW plossls. If you ever upgrade your scope, you can take these with you.

I think the Soul nebula looks like a teddy having a ciggie! (image by NASA)

Right! Thanks. That's my Christmas pressie sorted!

Refractor 'Lickers', surely?

It might be an important consideration for Christmas - the 150 Heritage is in stock just now at FLO.

Nice. The North polar hood is showing a lot more than I've seen over the past few months. Winter is coming, for Mars!

Atmospheric Dispersion? As in "Atmospheric Dispersion Corrector"? https://www.skyatnightmagazine.com/reviews/accessories/zwo-1-25-inch-atmospheric-dispersion-corrector-review/

Yep. The second image shows where the tripod adapter will attach

If you had to refocus to make the edge sharp, then it's going to be field-curvature, rather than coma, I think.

Well, I thought this single thread would save me posting lots of different ones for each sketch! It's been 4 weeks now, but at last a good night for observing! Mostly done at x150. It appeared calm but didn't really take much more magnification. Seeing wasn't too bad, with plenty of opportunity for fine detail - although it did appear to be degrading as time went on. Afterwards I tried a quick stacked video with my phone, but it wasn't great.

Ever thought of a RACI finder?

Thanks all. I had found an Altair 2" Dielectric with 1.25" adapter going secondhand for not too much. Thought it would work here with 1.25" EPs but also a keeper for future scopes. The diagonal with the scope is the cheapy plastic one that everyone recommends is replaced.

Hi, Now I've become familiar with Newtonians, I get a Mak to start the learning process all over again. It's only a wee one - Skymax-90. A quick look at Mars last night between the clouds and I'm hoping to get a little more use out of it this weekend (weather permitting). I have the eyepieces from the current 8" dob. I believe it has a M44.5x1.0 Maksutov thread on the back plate and a visual back that allows for a 1.25" star diagonal to be fitted. The actual hole in the back plate is only 18mm diameter (the internal circumference of the end of the baffle tube): Now - I realise that this is a small Mak, but the thread on the back isn't much different from an SCT thread size, I understand, and adapters are available. I have the chance to get a reasonable 2" star diagonal. Is this appropriate for a little Mak like this? Would it just be a waste and would 2" EPs just suffer from vignetting? I know it might be overkill, 2" attachments on this scope. But I would hope that anything I get would transfer to other scopes later. Perhaps the 2" diagonal with a 1.25" adapter and stick with 1.25" EPs would be fine? Cheers

Telrad and RACI. Did someone above say they had a Telrad going spare?

Do you find you need an RDF to go with it? I have trouble aligning my dob's RACI without the Telrad.

Hi, A question for anyone with a 90 Mak. Wide angle EPs aren't possible, so the available FoV through the scope is limited with a slow f13.8 3.5" scope. It has an RDF, but is a straight 6x30 a better option as the finder? Anyone with any experience of using both types of finder with a small slow scope? Cheers

I love how they intend to measure the mass of the sample they've taken, once back orbiting the asteroid. Osiris-Rex will extend the sample arm and then go into a spin, measuring its angular momentum. They'll compare this figure with one taken when they did this earlier with no sample, and the difference will give them the mass of the sample. If they haven't got enough, they'll get some more in another TAG.