I would not get the 10x30, because at the 30mm is going to be a narrow apparent field of view.
If you are thinking about using a barlow pick the 8-24 because 4mm is a usable power.
If not get the 7-21 to get slight higher magnification than the 8.
Welcome to the forum.!
I am leaning towards the 8-24 because I am very pleased with my 6.5, so I don’t need the slightly higher magnification of the 7.
And thank you for the welcome!
10-30: 33-51 deg AFOV.
7-21: 40-57 deg AFOV. Smallest and lightest of the trio, may be better for the AWB focuser although others have reported no issues even with fairly heavy eyepieces (300+g). A bit cheaper than the 8-24. Stated eye relief a little lower than 8-24. 7mm overlaps with your 6.5mm. Good match for a small scope.
8-24: 38-56 deg AFOV. Larger, good eye relief (works well with eyeglasses). Costs a bit more. Heavier. Stops at 8mm so your 6.5mm is a useful jump. A more natural "transition" eyepiece between your 35mm and the 6.5mm. My vote is for 8-24. FWIW my SV406P spotting scope came with a modified version of this eyepiece (no filter threads), it works well both day and night with no SAEP, very easy to look through under all conditions
Svbony also has 2 new zooms:
SV191 9-27 (40-60 deg AFOV)
SV191 7.2-21.6 (42-65 deg AFOV)
You can read about them here:
I have eliminated the 10-30 based on several factors pointed out by you and some of the others.
I am leaning towards the 8-24 for many of the reasons that you have pointed out.
I looked at those new zooms, they look great, but I think that I will be happy with either the 7-21 or 8-24, for less money when the savings could go towards a nice 15-19 as has been pointed out.
What does “no SAEP
I have a Orion E-series 7-21mm which is the same as the SvBony 7-21mm and its a great zoom. I dont care for the 21mm setting since its to narrow FOV for my liking but if you have or buy a decent 20-25mm eyepiece then the rest of the zoom is usable. But I was surprised how decent the optics were even in the 7mm setting for a cheap zoom. I like having the zoom when I dont want to take alot of EP's with me or if its cold and dont want to take EP's in and out of diagonal. Everyone should have a zoom in the eyepiece case for multiple reasons, very useful at times.
I agree with you on the utility of a zoom. Yes, the optics typically aren’t as nice as fixed but they can be very convenient.
I am thinking that I can probably use my 6.5 HD60 with the zoom for a slim setup when needed.
I purchased a SvBony 7-21 last year, very disappointed with its functionality. Very stiff to turn and in cold weather, 40°F or lower, it wont turn at all. Appears that I am the only one that has had this issue from the threads I've read. YMMV. A couple of specs of dirt on one of the internal lens' that will come in and out of focus as you change FL.
Sorry to hear that you got a lemon! I see that a few others have also gotten units that are substandard. I will be on the lookout for any issues with whatever ep I end up with. May I ask, why didn’t you return yours? Was it a used lens?
I have the 8-24 and have used it in my OneSky. Optically it's not bad, but in the f5 OneSky it will show astigmatism at the edges for sure. It is greatly improved by placing it in a 2x barlow.
I do not recommend any zoom like this for the OneSky, due to the helical focuser. You will have to use 2 hands to focus or change magnification.
From your list, you need an eyepiece between about 9-15 mm. For medium power I use a Nagler 13T6 in my OneSky.
Thank you for your input. I understand how the helical focuser does make it challenging to use an eye piece that twists in use. What would you recommend?
I would have to find a particularly good deal or a reasonable facsimile to get a Nagler 13
Any suggestions for reasonable facsimile, even used, for a medium powered ep? Based on what is being suggested, I think I am looking for something in the 16-18mm range. I am happy with my lowest and highest magnification eyepieces for now. So I think getting the zoom and a medium powered ep will work for now. Later, I will look for something in the 10 and 20-25 range to replace the stock eyepieces.
You should do more observing to figure out:
1. Which magnification you like to use; and
2. Which eyepiece you dislike the most in terms of AFOV, edge performance, eye relief, ergonomics etc.
That will guide your next purchase. Your collection (6.5,10,25,35) is a good spread, the only gap is at 15-18mm, otherwise the jumps are 50% (6.5-10, 25-35).
The most obvious purchases:
1. Zoom (simplicity, realtime splitting of doubles, different experience etc). Already discussed in previous posts.
2. 15-18mm. Many choices here.
- For semi-premium, I suggest the APM 18mm UFF, the Svbony version which I own is much cheaper than the rest, as low as USD 60 from Lazada. Other choices: Paradigm/Starguider/Xcel LX are in the same price range, you can search CN for reviews (but people mostly prefer other focal lengths in these series).
3. Upgrade an existing eyepiece.
- If the 10 is a Plossl, the limited eye relief and smallish AFOV make it a candidate for replacement. Semi-premium contender: APM 10mm UFF, as low as USD 33 (Svbony branded) from Lazada. I plan to buy this myself. Other well-regarded mid-range choices: 9mm Meade HD-60 / Celestron Xcel LX.
- The 25 and 35 should be fine. If you want to spend, a 24mm eyepiece from ES or APM can replace both the 25 and 35. More affordable choices: ES 26/62, 25mm Meade HD-60 / Celestron Xcel LX.
Thank you! A lot of useful information here. I agree with your assessment of the situation and it is also the same or similar to the rest of the advice here.
I already know that my least favorite eyepiece is the stock 10mm. I much, much rather use my 6.5, and the wider FOV is one of the reasons why. I just used the 6.5 for the first time last night and I was very impressed and pleased by how easy it was for me to track Jupiter with the 6.5. It was much harder to follow Jupiter with my 10.
As you can see from my earlier comments, I agree about needing something in the 15-18 range. I am already looking around and doing some research.
Good point about the helical focuser. Was not aware the OneSky had this kind of focuser.
What are the other types of focusers that can be used with the OneSky? I have already experienced a couple of “challenges” with it. I have already applied the Teflon tape and it does work well. However, with a couple of my lenses they really don’t achieve focus until they are almost screwed all the way up and almost out of the helical focuser. My solution has been to use a spacer that I made from some closed cell foam that holds the eyepiece up a few mm from sitting flush in the eyepiece holder. This seems to work by changing the focal distance or something that I don’t really know about…this just works for me.
All of the budget zooms mentioned will perform about the same at the edges. It won’t be terrible, but not perfect. I would just pick the zoom range you want.
You don’t need an expensive barlow. This would be the least noticeable after telescope optics, collimation, seeing, and eyepiece. A $40 barlow will be just as good IMO.
I wouldn’t invest much time, money or energy on trying to take pictures through this scope. It’s simply not designed for this.
From what you’re saying about the eyepieces, it sounds like you are enjoying long eye relief and larger appearance fields of view, like most of us. Look for eyepieces with large eye lenses. The Astro-Tech Paradigms are a good budget choice.
Good advice, thank you. Yes, you are absolutely right about enjoying larger fields of view. What a joy it is using my 6.5 that has a wider view than my 10mm
Edited by Bener, 25 July 2021 - 12:44 PM.