Aaf146

Hi guys, I have a question. I have an 8" dob and am going to make a filter using solar film.

Is it worth making one for the full 8" aperture or will the off axis aperture stop be better for it. 

I don't know how much more detail will be gained from using the full aperture so any advice would be greatly appreciated.

Thanks, Adam

8 hours ago, PeterStudz said:

I have an 8 inch Dob and I use binoculars before most sessions. As well as being fun and something in its own right it helps me:

1. Relax and get my eyes use to the dark while the Dob cools. Relaxing is just as important as getting eyes in tune with the dark.

2. See what the quality of the sky is like.

3. Plan star hops. Since I’ve had binoculars every new star hop is planned in binoculars first. It’s so much easier and saves time at the finder & eyepiece.

And some objects, like open clusters, actually look better in my binoculars than they do in the Dob. So I end up seeing more than I would with just the Dob. 

I do have some binos as well and they definitely get used. I do like you and check out my star hope first, then if I struggle to find the object with the scope I will go back to binos to try again.

5 hours ago, badhex said:

From my personal experience, I would say that if you can't go for a ~100mm doublet straight away, going for ~70mm doublet definitely makes sense. I would however probably not go from 70mm to anything less than 100mm - I have 73mm, 80mm and a 102mm refractors and the 80mm never gets used any more. It's a lovely scope but it doesn't show significantly more than the ZS73, isn't as portable as either the ZS73 or 102 with their retractable dew shields, but yet requires a mount which is about the same class as that which the 102 needs. 

The smaller scope I have is a William Optics ZS73 F5.9 doublet which I can strongly recommend for the very high quality of the optics and build, and also how compact it is for storage and transport purposes - crucial for any grab and go. Cooldown times are minimal, the optics are remarkable - it really punches above its weight and is surprisingly good even on the planets despite the short focal length. Thanks to the retractable dewshield I can fit the scope, mount (AZ-GTi), diagonal/eyepieces and other accessories (basically everything except the tripod) in one backpack making it easy to store, and simple to take to other, darker sites when required which I have done many times. Once set up, the whole thing can be moved with one hand, although I usually use two for safety's sake! 🙂

I also have a TS-Optics 102 F7 ED (identical to the Starfield 102 F7 ED) which I got at the end of last year. I would not necessarily consider this an upgrade per se, as the larger size means it's still easily movable but will require a sturdier mount and tripod than the ZS73 and is therefore a bit less portable overall. It also takes a bit longer to cool down, but not drastically. It's a fantastic scope, great build quality on par with the ZS73, and due to the increased aperture obviously will show you quite a bit more. As pointed out by many others here in SGL, this class of refractor also has the advantage of being able to give reasonable widefield views (about 4 degrees of sky) at one end, and 200x at the other, skies permitting, which makes for a very flexible observing experience. It was was this point that convinced me to take the plunge, and I have not been disappointed.

I tend now to use the 102 more at home and the 73 for travel or out of the house. If I had to choose only one, I would be torn - and reluctantly say the 102mm due to the larger aperture and observing flexibility, but they are both really very good scopes, and you would definitely not be disappointed with either.

Pictures of both scopes below for reference (plus the ZS73 in backpack mode) 

Yeah I didn't mean go up 10mm at a time, more than I'll start off small and then jump up in size as and when I can. Really nice scopes btw. Hopefully one day for me haha

1 hour ago, Ags said:

I have the William Optics 66 ED and pleased with it, meaning of course I want to upgrade 😆 

Currently looking at the Explore Scientific 80 f6 triplets - the basic version is not a lot more than the Stellamira doublet, and they are very short and light tubes so good for travel.

When does the upgrading ever end though. That's the trouble.

1 hour ago, KP82 said:

Re: Bresser AR102xs. I had one and used it for about 6 months two years ago. Like others have said the CA was surprisingly well controlled for a f/4.6 achro. However don't let the use of unknown ED glass fools you, it is still a very fast achro. If you intend to use it other than widefields, you'll need to set your expectation straight. Personally I'd never go above 90x in mag (that was with a 5mm BST) or otherwise everything felt soft/bloated. 

A 60 - 80ED would be my recommendation if your budget allows. Just remember most of the 80ED f/6 scopes are triplets, so they will cost quite a bit more and be heavier than the doublets. Stellarmira offers quite a few good options: 66ED f/6 and 80ED f/6.25. The build quality is a notch above the Skywatcher equivalents.

Yeah it'll definitely have to be a doublet. Triplet is outside my budget, plus my wife may just bury me under the patio if I spend too much.

I was thinking f4.5 seems way too fast, even with ED glass, glad to have my suspicions confirmed. 

1 hour ago, Ricochet said:

The 72ed certainly fits the bill for that. When I started looking at the stats the F7.5 80ED is quite a bit bigger than the F6 72ED. An alternative option which falls between the two is the Stellamira F6 80ED. 

Yeah, there are a handful of f6 80mm lurking about. I'm tempted to go for a 70 ish mm doublet and then at a later date I could possibly upgrade to 80, 90, 100.

On 22/05/2022 at 21:44, Ricochet said:

I recently went for a 72ED as a grab and go for those nights when I haven't got the energy to get my 8" dob out (and put it away again). I considered several 80-90mm ED scopes but in the end the weight and maximum field of view were probably the things that swung the decision. I have been very impressed with it optically so far, lunar views are sharp and it can take quite a high magnification relative to its size. Of course a bigger aperture would show more with regards to DSOs but that also means a longer an heavier scope, potentially with more substantial mounting requirements.

That's my thinking. I'm on my feet for around 12 hrs a day and don't get back from work till half 10 at night so I haven't always got the energy to take my dob out.  It'd be nice to have something I can take out, look for an hour and carry back in in one go, nice and easy.

On 22/05/2022 at 19:21, iapa said:

There are many 80ED refractors, e.g. Skywatcher have two lines, Esprit and Evostar (there was also the discontinued Equinox), at different price points.

Hence my question about budget.

I may be missing something when people say ED80 as something being a specific model.

 

Well I mean something in the 450 odd pounds region. Of course I'm not going to get an ES or Tak 80mm for that sort of money but svbony, skywatcher etc are all around that price point depending on where you look.

17 hours ago, iapa said:

You have mentioned a couple of options, but what sort of budget do you have?

An 80ed is probably my upper limit. Of course if I find one 2nd hand all the better.

49 minutes ago, Merlin said:

What about a 130/f.5 Newt on a light alt/az?

 

 

Tbh I am hoping to get a refractor as they don't require collimating, among other things. Plus it is getting a little on the large side for me as my small setup.

Thanks anyway

Adam

28 minutes ago, vlaiv said:

https://www.firstlightoptics.com/evostar/sky-watcher-evostar-90-660-az-pronto.html

Do note that Skywatcher models will be more expensive due to announced 10-15% price increase in new batches. Current prices will last with current stock.

Above scope is nice compromise in everything - price, aperture, F/ratio and hence color aberration, weight ...

I personally only object it having 1.25" focuser instead of 2" (which 100mm models have).

Have owned st102 and it is not all around scope. CA is just too large for any serious higher power viewing. It itself might not bother you - but it simply blurs high power detail. 100mm can show quite a bit detail on planets / moon - but not so with st102.

Bresser ar102xs has similar amount of CA as st102. Although it has ED glass - it performs similarly to st102 because of faster F/4.6 ratio (which is hard on eyepieces).

Here is nice comparison between two scopes (and third one for good measure):

http://interferometrie.blogspot.com/2017/06/3-short-achromats-bresser-ar102xs.html

102/660 is the best due to it being slowest.

90/660 is faster than this still (at expense of some aperture).

In any case - you can control amount of CA for high power viewing by using aperture mask. Here scope with largest focal length has an edge. 90/660 can be easily turned into F/10 instrument by using 66mm aperture mask (and it will have similar performance on planets as for example 70mm ED from SW).

Thanks for the detailed reply. 1.25" isn't a complete deal breaker as most of my EPs are that size. I only have 1 2" and I don't think it'd work well with such a fast scope anyway. 

3 hours ago, Dan_Paris said:

 

A 8" dob is very quick to set up, do you need something smaller and lighter ? 

 

In that case, if your budget is limited, you could build a travel dob mount for your mirror, something like this

 

https://www.webastro.net/forums/topic/193553-strock-2001000/

 

 

 

 

 

Yeah, it's easy to carry outside, but it takes time to cool down. Plus I can barely fit it in my car so am looking for something smaller and lighter as you say.

Plus collimating it is a pain every time I go out with it.

1 hour ago, Alkaid said:

I have an st102.  Does low power star fields extremely well. It’s a sky-surfer this one, the larger objects such as M31 and M45 are good at x20, especially from a dark site.  Moon is awash with CA, don’t let anyone fool you into believing it’s a general purpose scope...cos it’s just not geared for solar system use and I daresay that the figure of the lens, while acceptable at low power, does not cut the mustard at higher powers.  (Being F5 doesn’t help either). I find about x50 to be the max with mine.  If you fancied something general purpose then the Apo’s are the way to go.

I'm by no means a perfectionist as I've only used cheap refractors and reflectors up to now so a bit of CA won't bother me but might have a look if my local observatory has a few different variants to try before I make a definite decision

58 minutes ago, MalcolmM said:

I had an St102 and thought it was grab and go untill I bought a 60mm scope. 60mm and an appropriately small tripod is a one handed out and observing in 10 seconds grab n go. 100mm with the necessary larger tripod is just more awkward to manoeuvre out doors and carry. But I appreciate that everyone has a different take on what is grab n go size

Malcolm

I'm just looking for something much easier to take out, when I haven't got as long, than my 8" (with cool down etc). That's why I was thinking of the 70mm ed, 80 is a little bit out of my price range unless I find a decent deal 2nd hand (which I am still looking at) but fingers crossed. 

If not I will probably go with the 100.

18 minutes ago, johninderby said:

I did use the xs on the moon where it gave nice sharp views but with some fringing around the limb and pn Planets it was not too bad so long as ypu didn’t push the mag too much. Bit ot is just an achro although a nice one so be be realistic in your expectations.

Made a great white light solar scope with a Baader solar film filter. 👍🏻

Achros can be exceptional scopes if they are long focal length. My ScopeTech 80 f/15 gives amazing lunar and planetary views. A version is also sold by Takahashi  which tells you how good it is..

https://www.firstlightoptics.com/scopetech-telescopes/scopetech-stl-80a-maxi-80mm-f15-classical-refractor.html

I'm hoping to do some white light solar observing as well so that's good news. 

I'm not expecting something outstanding tbh on the moon or planets with such a short focal length. Just enough so I can actually see some slight detail. 

Thanks for the help, looks like this scope is definitely in the running.

Adam

33 minutes ago, StarryEyed said:

Buy a cover for the dob and leave it out. If you cant do that put it on wheels. Otherwise the 102/600 which you can also stop it down to 80 or 70 if you use it on the moon which will sharpen it up a lot.

Neither is practical. My garden isn't flat enough for wheels and I wouldn't want to leave anything outside I cared about losing. Stopping it down might be a good idea. Thanks

40 minutes ago, johninderby said:

Had a Bresser 102xs and CA was surprisingly well controlled for a fast achro. The Bresser achros have better optics than the SW ones as well as better build quality and a great CNC R&P focuser but would recommend getting the dual speed knob option.,

Myself I would go for the Bresser 102/600 as it will have less CA although as mentioned the xs isn’t too bad.

Easy to fall o to the just spending a bit more will get ypu a better scope trap. Where does it end? 😁

That's always the problem isn't it. Something will be 50 more than a different one, but an even better one will be a little more than that and suddenly you have to sell a couple of children just to pay the mortgage. Thanks for the advice. Did you ever try the xs on the moon or moderate power on the planets.

28 minutes ago, Ags said:

If I am not mistaken the xs does use a low-dispersion glass element.

It does but I've heard online from a new people that bresser don't give details of what type of glass they used, hence the hesitancy.

Hi guys, I have an 8" dob but am in the process of looking for a nice grab and go scope.

The problem is my budget is quite limited. The obvious choice would be an st80. Then I saw the st102 is not that much more expensive. I've had a look around and seen some others that might fit the bill.

So there's the bresser ar102xs. Nice and small, easy to mount, some lovely wide field views. The problem is its focal ratio is so fast. Has anyone used this and is the chromatic aberration as bad as I imagine. Plus there doesn't seem to be any info on what Ed glass is used, which seems quite suspect.

Then there's the st102 which doesn't have any ed glass but slightly longer focal ratio which might balance it out. Again its small and an easy grab and go.

Or would it be better to get something for a similar price with proper ed like a skywatcher 70mm. Obviously it has a smaller objective lens but again will offer nice wide field views and should suffer less from CA due to the better lens.

If anyone can help me with this it'd be greatly appreciated.

Adam

3 hours ago, Franklin said:

Agree. You will not be impressed with the Celestron 'Cometrons'. They use the cheaper Bak7 prisms and the field of view is smaller, even though you will see more in that fov due to the smaller magnification. I had a pair for while and I'm sorry to say, but they were like toy binoculars. However, for £50 I picked up a new pair of Revelation 8x42 roof prisms with green rubber armour, like bird watching bins, and they are actually superb. Can't fault them, very pleased and the views are amazing. I think they retail for more than what I paid and the £50 was an end of stock deal. You can pick up a pair of vintage 'made in Japan' 7x50 binos off fleabay for £20 or there abouts and the optics will be smart as long as they're clean and undamaged, but they are quite chunky and heavy. I got some Vixen 7x50s for £16 and they're a great optic but heavy. I prefer my Ultima 7x42s, nice and light.

13 hours ago, apaulo said:

personally i wouldnt buy new bins for £50.  i bought a pair of used 7x50 zomz on ebay that i use at sea. they are very good a lot better by far than what youll get for 50 new.  from past experience i would recommend  them. hope this helps. paul.

Thanks for the replies. I'm wary of buying 2nd hand off ebay or similar sites as I've been bitten before buying 2nd hand. 

I got some but they were out of collimation or alignment and the screws to adjust were rounded off so they were pretty much useless. I will have to see if there are any I can go and look through first before buying.

Thanks for the replies, Adam

Hi guys, first time posting on here. 

I've searched to see if anyone has already asked this question but couldn't find anything.

I have a pair of cheap 10x50s already and enjoy them but am looking to get some 7x50s now for a slightly wider fov. I have a very limited budget of £50. I've seen the celestron cometron which seem respectable. 

Does anyone have any experience with these binoculars or any advice on other binoculars in a similar price range that might be a better choice.

Thanks, Adam