pregulla

I have found 11-12mm range most useful for DSO. I usually use 35mm Aero ED as a low power/finder and then switch to ES82 11mm for most objects. Some objects benefit from 16mm or 24mm, but 11mm does the bulk of the work :).

BTW for planetary I prefer zoom eyepiece + barlow. Best magnification varies with seeing from night to night and zoom allows to get most of it. I quite often push above 200x on the Moon and Jupiter. On the other hand I found that wide filed eyepieces (ES82 11mm, ES68 16mm) show lateral color in the outer field so the useful field is pretty close to that of a zoom eyepiece.

There is a confusion between two things in this thread.

First - decrease in  image brightness as a result of increased magnification/decreased exit pupil. Everyone agrees on that, but this effect is not unique to Barlow. If you just use eyepieces with different focal lengths the effect will be the same - dimmer image at higher magnification.

Second is reduced light transmission due to extra glass added. With good quality Barlow this effect is too small for human eye to detect. It is unrelated to all the principles described above and this is what people mean when they say Barlow doesn't decrease brightness.

Lets say you use 20mm eyepiece. Then you add 2x Barlow. The image got 4 times dimmer because of increased magnification and say extra 3 percent dimmer because of light transmission loss. Now you just use 10mm eyepiece. The image is still 4 times dimmer compared to 20mm just without the extra 3 percent loss. If you compare 10mm to 20mm+2x Barlow you won't be able to tell the difference in brightness. So we can say Barlow doesn't decrease brightness, now that we have taken the effects of magnification out of the equation.

The article is poorly worded (or the author is decieving on purpose?). Doubling the magnification will reduce the brightness by a factor of 4 (or by 75%). It doesn't matter if it is done by using a barlow or a shorter focal length eyepiece. The article makes it sound like a barlow robs you of 75 percent of light that would be there if you just used an eyepiece, which is false. Quality barlow with modern coatings will only loose few percent of light.

I replaced mine with bellville washers. 16mm OD, 8mm ID IIRC. 3 in series on each screw, depending on how much travel you need.

Try rotating the laser or the cap inside the focuser. If it changes how your collimation looks you know they are off. 

You probably won't be able to tell the difference between 92% and 99%. Though I think Meade comes with erecting prism, then getting a star diagonal will be benefitial.

I woudn't bother with filter yet. It helps a little, but doesn't iliminate light pollution. With my 8" dob the difference is pretty marginal - it helps to bring out a little more detail or detect what can't be seen at all without a filter, but not even close to what it is like under dark skies. Plus with 70mm under light polluted skies you are pretty much limited to brighter clusters, and UHC won't help you with those. 

From a city (Bortle 8 ) with 8x42 binoculars Andromeda looks like very faint, barely detectable fuzzy patch, no core or other details. As skies get darker it gets brighter, larger and the core becomes visible

How long do you plan to spend there? For one night 3 hours extra sounds like a lot and I would probably settle on bortle 3. If it's more than that I'd go for as dark site as possible or you will keep wondering how would it be under darker skies.
 

Bortle 3 is the darkest available for me. I live under bortle 6 skies and the difference is huge. I can barely detect the milky way at home, at bortle 3 site it looks very detailed and impressive. My first night I spent more time with binoculars than a telescope. Obviously DSOs look more impressive too and fainter ones can be seen.

So I got 120mm in the end. AZ3 is pretty solid, at least at lower powers, but the balance is an issue. The scope will nose-dive near horizon and butt-dive near zenith. And that's before even getting 2" diagonal.  Seems like it should be decent enough if I can fabricoble a ciunter weight.

There are many good options. It all depends on what you are looking for. How much would you like to spend? How much eye relief you want/need? Do you observe with glasses? Do you prefer a zoom or single focal length eyepieces. How wide of a field do you want?

I would start with getting 2" diagonal if it doesn't come with one, 2" Wide filed eyepiece in the 30-40mm range, a zoom eyepiece and a quality 2x barlow. That will get you covered from low to high power until you figure out what your preferences are and have a better ideas what eyepieces will suit you best. 

If you buy used you can swap later at minimal loss.

I am using 40mm with mine. All 2" eyepieces I tried come to focus with it (Aero ED 35mm, Meade QX 26mm, ES82 30mm, SkyWatcher SWA70 32mm). I also use it with 1.25" to 2" adapter which is about 10mm tall and all my 1.25" eyepieces come to focus. I also know that 50mm was too much for SkyWatcher SWA70 32mm, I didn't try with others.

Having multiple eyepieces with cracks would make me wonder if I store/handle my eyepieces properly.

I also never came across eyepiece that I would describe as dirty on the inside. I didn't have a whole lot of cheaper eyepieces, 10 total maybe. Some may have had a spec of dust or flake of paint between lenses. But nothing so bad that I would call it dirty. I am sure there are some out there as a result of poor QC of the cheaper products, but they don't tend to be this way from my experience.

3 hours ago, Alfian said:

The  ST120 is noticeably bulkier than the 102 but will be fine on the AZ4. Dont know about the AZ5. The Aero 35mm is a nice EP but it will give a 7mm exit pupil at F5.  May be OK with nice dark skies and younger eyes than I have, just something to be aware of.

 

The 35mm works fine in my F/5 12". I may be loosing some aperture with it, but I don't notice any negative effects. I also have ES82 30mm, but I feel it's a "little" overweght for this task.

I think on steel tripod AZ5 should be fine. On the original aluminum tripod I am afraid 120mm will be too much for it. How is the AZ4 with it's original aluminum tripod? Overall I get a feeling from all the reading that AZ5 is better with short scopes. AZ4 is sturdier and more convinient with longer scopes.

Since I am getting AZ3 with the scope anyway I may try to make it work first. I have seen reports that after balancing it was acceptable for 120mm. If I was going to pay for the mount, "acceptable" woudn't be something I want, but for a freebie I will give it a shot.

ST120mm just shower up on a used marked locally. Comes with AZ3, but the price is right. For 120mm I feel less confident with aluminum legs, so I'll probably get AZ5 with steel legs, especially since the difference when buying just the mount (head+tripod) and not the scope combo is not that big.

OK, AZ3 is out of the question then. Turns out Telescope-Express were underestimating shipping costs for AZ4 (it's like 100 EUR extra), so AZ4 doesn't fare well against AZ5 price-wise.

Looks like AZ5 is the way to go.

Hi All,

I have decided to get a fast achromat to complement my dobs for low power wide field views. The SW Startravel 102mm seem like a perfect choice . I plan to get 2" diagonal for it and use it with 35mm Aero ED eyepiece (about 360g).

The question is what mount would be the best choice? I plan on buying from Europe, since buying locally is way too expensive and options are very limited. The options I have thought about:

 - OTA+AZ3 bundle, about 270 EUR. Cheapest option, but AZ3 seems like not the best fit for purpose. From what I understand it goes out of balance at higher altitudes and gets inconvenient to use. I may still get the package and upgrade later if I don't like it. The problem is I'll have to pay for shipping again. 

- OTA+AZ4/AZ5  with aluminum tripod. about 400 EUR

- Getting separately the OTA, AZ5 and stainless tripod: About 490 EUR. 

- AZ5 Shipped separately if I want to upgrade from AZ3: 257/288 EUR with Al/SS tripod

- SS tripod shipped alone - 143EUR

I am leaning towards getting the AZ5 with Al tripod. Should be fine for the Startravel 102. Upgrading to SS later will cost 50 EUR more than buying it straight away, but I will have the Al tripod too, so not too bad.

Any comments? Are there other options that I am missing? Maybe there is a different OTA that comes with better tripod and would make a better deal as a package (Something around 100mm F/5 - F/6, 2" focusser)?

Good job! But your setting circles are back to front. You either need to reverse the scale or put it on the bottom plate of the base. I prefer placing it on the bottom and putting a pointer on the top. This way the pointer is always at teh same spot relative to eyepiece.

Same focal length and AFoV doesn't nesessarily mean they are the same design. There is also Meade QX 2" 26mm, which is reportedly worse performer than the Panaview or Orion Q70. If you have F/10 or slower scope you can give it a try, with something like F/6 or faster I wouldn't bother.

21 hours ago, Raph-in-the-sky said:

And one more question: Am I right in assuming that any of these EPs will be better than my 8-24mm Celestron Zoom ?

I think that the Zoom will be at least comparable in quality, especially closer to 8mm. I personally would just use it and a barlow for anything under 15mm. Out of all the eyepieces I would just keep 32mm or 30mm plossl, 15mm Starguder, Celestron Zoom and the barlow.  The 25mm is too close to 32mm to be worth keeping IMO. 15mm Starguider will be wider than the zoom, but may be still close enough so you will keep using the zoom.

It's all a matter of personal preference. Some people don't like zooms and barlows and would prefer dedicated eyepieces for each focal length. In the end you'll have to try for yourself and find out what works for you.

I mostly use ES82 11m which gives me 136x. 

It is not only about magnification but also about exit pupil (focal legth of the eyepiece devided by focal ratio of your telescope). Generalyl larger exit pupil (lower magnification) gives brighter image, smaller - higher contrast. The sweet spot is around 2mm, or 16mm eyepiece with your telescpe, but the best way is to try for yourself and see what works best for you.

I would start with zoom eyepiece + 2x barlow. I like my Celestron zoom for Moon and planets. It works fine on DSO as well and will let you cover the medium-high power range without spending a fortune. After you have used it for a while you will have more clear understanding of what your needs and preferences are and where you want to upgrade, if at all.

Make a dedicated case for the finder, put your spare batteries there as you get it out. It's will remind you to turn it off as you put it back in, and if you don't - you have the spares

I have left mine on few times, not for too long - few days, maybe a week each time. The batetry is still alive. 

I think the problem with zoom binoculars is not the quality of zoom eyepieces, but with getting both to stay "in sync" while zooming.

41 minutes ago, Louis D said:

Eye relief became tighter on all eyepieces for some reason.

Makes sense. Diverging light cones increase eye relief. It will be longer in faster scope for the same reason it is longer when using barlow. In slower scope the cones are closer to parallel and eye relief will be shorter.

On 12/06/2019 at 06:06, Louis D said:

I think the Paracorr is supposed to go first since you need to maintain a constant distance between the primary and the corrector lens (ala the SIPS version).  I can't reach focus with a barlow or telecentric magnifier when using my GSO CC, so I remove the CC since slowing down the light cone greatly reduces coma anyway.

My understanding is that Balrow helps with eyepiece aberrations (for ones that struggle in faster scopes), like astigmatism, but it doesn't help with coma or any other aberration that comes from the objective.