Pixies

Hi. As you say, the secondary holder and the assembly attached to the vanes should be roughly 'parallel'. You can normally check this by seeing that the 3 adjuster screws are close to even levels. Another way is to wind them all out and tighten the central screw, bringing the secondary back up the tube. Bring it as far back as it can go, then do the opposite, but making sure you tighten the adjusters by equal amounts as the secondary moves back down the tube. That way, it should remain parallel. Can you carefully get your phone inside the tube and take a pic of the secondary base?

How is the hyperion in your fast scope? A friend has an f5 and says the Baaders suffer from a lot of distortion.

But to make it clear to anyone wondering. The majority of modern Newtonian reflectors have this offset built in to the secondary mirror holder. You don't need to worry about it when collimating - just align the secondary concentrically within the focuser. As @johninderbysaid.

Not wanting to take the OP's topic off-track. A Peter says, the issue is that when you intersect a cone, the ellipse is not centred over the axis of the cone. If you imagine a cone of light from the primary up towards the secondary, you will either need an oversized secondary mirror to capture the full area of the intersection, or an offset elliptical secondary. Follow this link and find the interactive diagram at the bottom of the page: https://www.geogebra.org/m/NnxHw6gY If you rotate the image so that you are looking down the axis of the cone, the elliptical intersection is offset. the faster the scope (the shorter the cone) - the more the secondary is offset.

Nope - just applying Mire de Collimation to the original image. It's a useful way of checking concentricity with an image from a collimation cap.

Hi, You need to make sure that the secondary mirror is directly under the focuser (and rotated to face it) before you try and centre the image of the primary in it. In Astro baby's guide, that's "step 2" with the coloured paper. It's distance up/down the tube looks pretty near, but you need to 'lower' the secondary using the 3 adjusting screws. A long Cheshire will help here, acting as a sight tube. You can use it to indicate how concentric you have the secondary. For example:

There's a very useful sticky thread that will help:

Hi, Having just been diagnosed with mild astigmatism (-0.5 in my observing eye), I realise why my 30mm EP isn't performing too well for me. I didn't like wearing my specs when observing before, so would like to avoid having to wear the new ones, too. I just saw this diagram from @Ricochetin a previous post: So a 4mm exit pupil is the point that astigmatism will show for me. That'll be a 24mm EP in my f6 dob. Now - can anyone here with astigmatism confirm how that chart works? If the exit pupil is on the line between grey and blue on the graph, is that likely to still have some visible aberration? Would I be looking at a point a bit further into the blue to make sure I won't suffer from astigmatic views? E.g. a 22mm EP? I guess I'm going to be looking for a wide FOV eyepiece, around 22-24mm. An Explore Scientific 24mm 82deg will have a very similar AFOV as my 30mm OVL Aero. Any other suggestions around the 2-ton mark?

I find it only reliable for a day or so in advance. You can use the more distant forecasts to get a rough idea of the likelihood of clearer weather, but not much more than that. Let's face it - how many weather forecasts are accurate more than a few days ahead? Certainly not accurately enough to be able to specify exact cloud cover

OK. I have issues too. It's fine with my specs on (shortsighted) but without. I can just barely get the crosshairs in focus when the finder is at infinity. I notice that when I look through the EP, I have to rotate the reticle focuser to the very end in order to focus on it. So I thought I'd have a go with the above. First, unscrew the nose piece: The plastic reticle is held in place with a lock ring. Undo this using either a spanner wrench (the correct way), a small screwdriver (the risky way) or a long fingernail. Now the reticle can tip out. The etched cross is on the outside, I flipped it round and reassembled it, which is just the above in reverse. I haven't used it in the finder yet, but I notice that now I can adjust the reticle focuser and reach focus on the crosshairs (without specs) and still have a little more focus movement to play with.

See these 2 small screws: fit the bracket there using these slots: et voila, something like:

It will be central. The mirror is offset in the holder. As per the AB Guide, tighten the vane bolts so that the central secondary adjusting screw is dead centre.

Celestron appear to have chosen a selection from their range of beginner - lower-intermediate scopes and added the StarSense setup to them. StarSense is much more than a gimmick. It isn't a basic star-map app with a compass/accelerometer to detect direction. It is an actual plate-solving system, which uses the mirror in the phone holder to direct a view of the stars. The app analyses the star patterns and works out where it is facing. A few on SGL have bought the cheaper models, removed StarSense for their own scopes, and passed on the remaining scopes to family members. The app requires a license key that comes with the kit. I recon that if Celestron marketed the StarSense kit seperately, it'll make a killing. So, if you really want StarSense, these scopes are what is available. If it's not that important (ie. you are happy to learn how to find things in the night sky and locate them in the scope yourself) you should be looking at other options. Although there are other GoTo systems available (at a price).

If you're a DIY type, here's:

Total lunar eclipse Nov 1975. I was 9 and my brother and I were allowed to stay up and watch. I had always been interested in the stars, but this was the first time I was aware of the 'mechanics' of what was happening above us. It made a lasting impression. Hale-Bopp too. I got so excited seeing it from central Edinburgh (after a night out and a few drinks) I called loads of people I knew to tell them how amazing it was. The next day at work, I was given the nick-name Cosmic. The image from my profile is a view of the first time I saw an Aurora from the beach at the end of my road. Of course the image is brighter than was was visible to the naked-eye, I could still easily see the green layers, but also movement as well as the vertical patterns. I realise that none of the above were seen using any optics at all.

Yes. You should at least check this scope out. Lots of good reviews on this site. It is currently in stock in lots of shops, too.

My advice - nearly every scope mentioned above will be great. All have strengths and weaknesses and it's not until you've had some experience yourself that you will learn to know what you want. Pick one you fancy. You'll have a great time with any of them, esp if you have dark skies.

Hi. Like this - with the 2" adapter removed for clarity:

It astounds me why Bresser supply that cheap plastic finder, when everything else is high quality. Even the supplied starter EP isn't bad.

Did it! Started early yesterday evening and bagged Jupiter and Saturn before they dropped too low. I felt I needed to use some kind of optics, rather than just naked eye, so grabbed my new Skymax-90 and checked them out before dinner. Later that evening I got the dob out for the further planets. Observed Mars first, and was planning to do some sketching later as the forecast had been good for up to 1am. Then on to Neptune. I just found it but high clouds were coming over and I had to call a halt as things got worse. However, at midnight the clouds were gone. So I found Neptune again - much clearer this time. Then Uranus, which was a little tricky to find as the moon was starting to wash out the sky for the initial star-hop. I thought I'd spend some time with Mars, but the seeing was pretty poor, due to high winds. Then to bed with the alarm set for 6 ready for the inferior planets. Up early for me. Snuck out with my 10x50 binoculars. Venus very conspicuous, but to find Mercury I needed to head down to the beach and try and roughly work out it's location using SkySafari. I managed to bag it around 6:20. Around 4 degrees from Spica, both visible in the brightening horizon. That's the first time I've ever observed Mercury. It felt similar to the past summer's Neowise hunting, scanning the horizon with binoculars at the beach, A bit chilier now, though!

They are in stock. FLO A have had them in for a few days. Early Christmas?

Hey - @merlin100 I did the same a while ago to my Bresser: I have thumbscrews that fitted (M4x45mm) plus M8x50mm stainless steel washer. They could well be the same size. Perhaps someone with the same scope as yours can confirm. If you want them, I'll send them to you. PM me if you're interested.

In 10x50 bins, that's exactly what it will look like.

probably having a 'vape'!