Pixies

I thought I'd do a little subjective testing with a pair of Skywatcher starter EPs that I had in the box of unused stuff. I had the little ST80 out to look at the recently brightening nova, RS Ophiuchi. I thought I'd compare the view of the double-star Albireo with some different EPs. Now, this refractor is short and fast, so a little taxing on EPs, also I don't use my specs when observing and I'm a little astigmatic, so the 25mm EP views will suffer a little from my own shortcomings. The sky was still a little light when I started but I completed the comparisons within 30 minutes and went back over the different EPs, so there shouldn't be much difference in sky quality. 25mm: ===== 25mm Skywatcher. Very adequate view but with strange effects at the field stop. The sky was still a little light when tested, but approaching the field stop, it started to dim and to fade to black. But beyond that, some reflectivity showed as a bright ring outside the stop. Made a very strange border to the view! 25mm Bresser super plossl. Comes as the single starter eyepiece with Bresser scopes- I think this is a GSO EP? Very lightweight compared to the Skywatcher, but a similar quality view but without the odd field-stop. Both show astigmatism off-axis in the F/5 scope and my eyes aren't the best with this 5mm exit pupil, either. But the view of Albireo starts to become distorted further from the centre of view in the Bresser than the Skywatcher. 10mm: ===== 10mm Skywatcher. The (in)famous EP in question above. Absolutely beautiful view of the orange/blue double star in the centre of view. Clear and sharp and fantastic colours. But... (noting again this is an F/5) astigmatic distortion starts showing at only a third of the way out from axis centre to field-stop. From around two thirds out, the distortion makes the view worthless. Now, I don't have any other 10mm eyepieces, but for comparison: 12mm BST Starguider. Sharp and clean at the centre, perhaps slightly not as colourful as the 10mm Skywatcher, though. Much wider FOV (60 deg). Pretty much astigmatism-free but field-curvature showing in this short refractor from two-thirds out from the central axis. Re-focussing cures this and the double-star can remain distortion-free to the field-stop with a little focus adjustment. 8mm University Optics Ortho. Similar view to the 10mm Skywatcher on-axis, but a little dimmer with the higher magnification. Astigmatism starting to show from 50% out but not to the same extent as the 10mm Skywatcher. Useable view to the (admittedly narrower) field stop 8mm Vixen LVW. Yes - chalk and cheese, I know. 65 deg FOV. Sharp, bright and colourful view. No obvious astigmatism or field-curvature to my eyes. Albireo sharp all the way to the very clean field stop. What does this prove? You get what you pay for, generally. But as @John mentions, it's probably a law of diminishing returns. The Vixen LVW was £200 new, although not produced now. Is it worth £180 more than the 10mm Skywatcher? I paid £80 for it. Is it worth £60 more than the 10mm Skywatcher? When I first started, would I even have noticed much of a difference in the view between them, apart from the obvious FOV differences? That and the size and weight!

Mind you. I've used the 'starter' 25mm Celestron EP - the plastic 'terrestrial' viewing one, and the only place that belongs ceratinly isn't a telescope!

I've heard people slag off the 10mm basic Skywatcher EPs, and others say they are OK. I wonder if this is a matter of poor quality control at this price-point and their quality is variable. I have a couple somewhere gathering dust (from secondhand scope purchases). I'll need to compare them.

Looking at the specs, these look incredible value! One question, @FLO, how do their focusers behave with a DSLR trying to achieve focus?

Looking at the AAVSO chart. There are some visual observations (bino and naked eye) estimating 4.5 - 5.0 from the past 12 hours or so. We've had cloud, mist and torrential rain all day, but it's startong to clear up. Some forecasts are saying clear spells for an hour around midnight! Fingers crossed. Thanks (again) to @JeremyS for the heads-up!

That's the internal reflection within the baffle tube. I imaging the 'diamond ring' will test any scope's internal reflections!

BST Starguidsers are frequently recommended. Most are good at F/5, although the 18mm is a bit soft at the edges even at F/6. The 8mm and 12mm are the best.

HI, Your 300 Dob has a focal ratio of F/5 (focal length divided by aperture). So it's pretty 'fast', meaning it's a light bucket and great for getting bright wide-field views. However, the faster the scope, the more demanding it is on eyepieces. That's because the eyepiece is trying to present a precise image from a wider anglular range of light rays. The description of the Celestron Omni Plossls at FLO says: "Best suited for telescopes with f-ratios f6 or slower." - so I would say that your F/5 scope is bit too fast for your eyepiece. PS - These terms "fast" and "slow" really come from photography, where you are dealing with exposure times. It means less with telescopes and visual observation. PPS - hope this makes sense and not too much terminology.

I missed that! Not sure how. 🤪

Looks fantastic. Very useful format and I'll be getting one. If I can make 1 suggestion: how about an index on the constellation name?

Mine (Skywatcher Strartravel 80) has rings and a longer dovetail - but hat's how it came secondhand. It's a great pairing with an AZ5.

Yep, thanks. It shows the star, but the info is still different. But yes, Sky Safari has an issue with it. There are several threads on Cloudy Nights about it too, as well as the Sky safari support pages. I've never come across a missing star in SS before, but I guess this must be linked to whatever data model they use to store multiple star systems. I do recall finding a mistake in angular seperation once before, though.

Very odd. In Stellarium on my laptop, it doesn't show. But it links Mizar with Alcor, and doesn't show the seperation with its close double.

Here's a useful tool: https://skyandtelescope.org/wp-content/plugins/observing-tools/jupiter_moons/jupiter.html I think you'll find it was both Io and Europa together!

It was the Darlington Sink Driver - TD62103P. I replaced it with a modern ULN2003A (£3 for 3) and now it works fine. The shudderring with the stepper motor has gone and it makes a full rotation every 10 minutes. Just letting you know in case anyone has the same problem. I have 2 spare ULN2003A ICs, if anyone wants one!

I find the problem with Skysafari (Plus) and Saturn's moons is that it displays them all the same brightness. Which can be a little confusing, at first!

Yes, that's all relevant. Collimation will get you as close as your system allows you too. The final test has to be a proper star test: the highest arbiter of collimation.

When you are adjusting the secondary with a Cheshire, to get the primary centred in it, don't worry about the mirror clips: just adjust it so that the crosshairs are over the doughtnut. It's the same thing. Anyway, I think your secondary might be tilted slightly, even though it appears a concentric circle. May I offer some advice? I found that the best start to collimation is to ensure your secondary mirror assembly is completely parallel (flat) to the spider assembly. You can do this by making sure that the 3 secondary mirror screws are protruding by the same amount, but this assumes everything is made to equal precision. This is what I did to fix my collimation woes: Keep loosening the 3 adjuster screws and tightening the centre screw. This brings the mirror back up the tube, away from the primary. Keep doing this until the mirror has been pulled all the way back to the top of the tube and is flush against the vane-assembly, with the adjusters just barely loose. This means that the base of the secondary holder is now flush with the assembly. Then - bring it back down the tube bit-by-bit, by loosening the centre bolt and taking up the slack with the adjusters. It's important to turn the adjusters by the same amount each, so that they all keep the same distance. If they are thumbscrews (like Bob's Knobs) use a sticker on each one with a line to show their positions. Then you know you are turning each one by exactly the same amount. Keep bringing it down the tube with the adjusters always equal. When you reach the correct position under the focuser, you know the whole thing is straight and level. Now, all you need to do is make sure it is rotated and facing the focuser correctly - so that the image of the secondary is concentric as above. Then you can take out the paper and make a final adjustment of the secondary tilt, to get the doughnut centred in the Cheshire.

A don't find that the Baader Neodynium helps that much with Jupiter. For Mars it's great - but that might just be me. As @Johnsaid, dark adaption doesn't help. I keep the kitchen lights on and occasionally look up. I've heard of people shining a torch onto something white and looking at it.

@Burns84 - can you get hold of a pair of binoculars? They won't have to be a super-duper astronomical set. They are an excellent way of practicing a star-hop before struggling with a straight finder and the reversed image. They are also a good way of observing something large like Andromeda. I can find this galaxy in summer's light skies with a cheap pair of 10x50s. Once the skies are dark, a smaller pair of bins will be fine. The Bresser dobs are great scopes but the basic finder that comes with it are rubbish. It's the single drawback of this manufacturer. There are plenty of posts in SGL about replacing the finder bracket with a Baader Universal one, so that you can use a better finder. I'm not suggesting you rush into further upgrades, but there will come a point when your star-hopping is limited by that finder. A lot of us recommend a red-dot/Telrad and RACI finder combination. And finally, the book "Turn Left at Orion" is an excellent guide to star-hopping and what you can see with different types of scopes.

Congrats John. Thanks for all the helpful posts over the last year. As well as all the advice, your observing reports are often drivers for me to try new challenges or just even get out there. Still not sure about the lens-licking though!

With my 8" solid tube dob, I have to re-collimate my primary about 50% of the time after a trip in the car. Never had to redo the secondary, though. That's with the tube across the back seat and normal roads. I check the primary every time I use my dob, home or away - takes about 20 seconds, including getting the Cheshire out of the box. If a quick adjustment is needed, and that's all I've ever had to do, it's a couple of minutes at most.

Here's a good guide to solid-tubed dob sizes, from the lovely Ed Ting. Orion scopes, but the sizes are pretty standard across most makes:

Yes, it will. If you stick an eyepiece straight into the visual back, the view will be reversed left<->right and also up<->down. Basically, rotated 180 degrees -just like a Newtonian. A mirror diagonal flips up<->down again, so only left<->right is reversed.

Oh Matron! Does 'terrestrial' viewing now mean nurses? (note - I make no differentiation between male and female nurses)