Optics Problem with new scope?
Posted 19 October 2003 - 10:50 AM
My initial impressions regarding the heavier mount and tripod are that there is simply no comparison. I would say it is 50% - 75% more stable than the AstroView system with this particular OTA. I was able to focus at magnifications up to 200x with very little vibration and able to remain “on target” during focusing at all times (something that at least my sample of the AstroView would not allow me to do). The OTA is the same scope, but rather than being painted white, it is finished in gunmetal gray to match the tripod and mount. One would think the optics quality would be very similar if not identical, right? I’m not so sure…
The first OTA had (in my newbie eyes) excellent optics. Very bright, stable images with surprisingly little false color evident even on very bright images. I was able to move my eye around the perimeter of the eyepieces and still maintain stable views. Star tests showed no evidence of astigmatism in the optics. Collimation was off significantly, but was quickly corrected with the adjustable lens cell. Fellow observers commented on the surprisingly good views it offered for the price. I would rate this OTA as 9 out of 10 for this achromatic price range. Unfortunately, these are "package deals" (with different color graphics) so Orion requires you to return the entire AstroView system to upgrade to a SkyView Pro system. Basically I had to return this excellent OTA for the system upgrade.
The new OTA appears to have some behaviors I can’t explain. (Collimation was also off on this OTA, but was quickly corrected with the lens cell adjustments. This OTA does not show signs of astigmatism either). Please remember, I have only had about 90 minutes with it in the field under far less than perfect conditions so far. There appears to be significantly more false color in this OTA (purple halo around bright objects). I would say it is perhaps 50% more noticeable than the previous sample. Secondly, there is some kind of strange optics effect occurring. My eye must be perfectly centered over the Plössl eyepieces (the same EP’s I used with the first scope BTW), or the image appears blurry. In addition if I move my eye toward the edge of the EP part of the image simply disappears as if it is being “cutoff” from the field of view. If I keep my eye position nearly centered, the image is quite good (similar to my first OTA sample), other than the increase in false color. Using the 2x Shorty Plus Barlow actually appears to reduce the image cutoff effect. I can position my eye less centrally when using the Barlow and not loose the part of the FOV image. I am hoping perhaps there is something that can be done to correct this behavior, as each time I ship something to Orion it takes a week to get there, a day or two for them to process the order, then a week back to me. Between waiting for tripod replacement parts and upgrading my order, I have been out of a telescope for nearly 4 weeks already. Do the OTA’s vary this much in CA, or is this an OTA with more serious optics problems? Any insight would be greatly appreciated…
Posted 19 October 2003 - 10:55 AM
Posted 19 October 2003 - 12:11 PM
Posted 19 October 2003 - 12:23 PM
Posted 19 October 2003 - 01:31 PM
I just placed an explaination about focuser adjustments under telescope equipment if you want to see how I do it myself, best part is you cant harm the scope and can always go back to the stock adjustments tho I doubt you would want to, Dave
Posted 19 October 2003 - 01:46 PM
Posted 19 October 2003 - 03:36 PM
Now that you mention focusser collimation as an important part of the optical train, it reminds me of 'the pinpoint stars across the field of view' that we talked about in another topic. I'm convinced of the necessity of perfect alignment for sharp views. I bought my 6" achro used, but it had a ronchi test (which showed very slight undercorrection) and the focusser was perfectly collimated by the shop. So I think it is a good thing that you brought this to attention as it is overlooked many times.
And Sal, I really hope you manage to bring the optical performance of your new tube back up to the level of the traded one. And yes, diagonals do vary in quality (and alignment), so there's hope.
Sky Watcher achromat 102F10
Posted 19 October 2003 - 04:02 PM
Posted 19 October 2003 - 05:02 PM
Posted 19 October 2003 - 07:20 PM
the optics shouldnt really exhibit bad blue/violet except at hi mags period especially being a f8 refractor. Might be a bad mainlens it happens. I had a Meade 90mm f11 that no matter what I couldnt get stars across the FOV without comas everywhere but at the center, I finally bought a new mainlens and sure enough it was suddenly ok, lucky for me as that cell was un-collimatable by me anyway. The focuser was really off on that one too must be a focuser trait of the low end Meades.
Posted 19 October 2003 - 11:02 PM
My eye must be centered over the Plössl EP almost exactly to see a good image. If I move my eye even the smallest amount off center, the outer edges of the image become “wavy” almost like poor seeing conditions, or like I am looking through a very thin layer of moisture. Stars near the edges of the FOV “smear”. I have never seen anything quite like it, so it’s hard to describe properly. However, if I reposition my eye carefully, the image snaps back into proper focus. I did not ever notice this type of behavior out of my previous 120mm. Again these are the same EP’s I used with the previous scope without problems.
I sure appreciate all the suggestions to alleviate the problem. They definitely helped reduce false color and spiking by getting the OTA collimated for the exact range I use the focuser in. Unfortunately, I am beginning to think I have gotten a bad sample in this OTA. I just can’t make any improvements in the optical distortions. So, once again, I will contact Orion to see what course of action they suggest…
Posted 19 October 2003 - 11:44 PM
Posted 20 October 2003 - 02:05 AM
Posted 21 October 2003 - 08:46 AM
Posted 21 October 2003 - 08:58 AM
Good luck with Orion, I hope they take care of you.
Posted 21 October 2003 - 09:02 AM
Posted 21 October 2003 - 09:38 AM
Posted 21 October 2003 - 12:21 PM
It amounts to lost productivity, unhappy customers, and higher costs in the long run, as well as a very busy repair center.
Posted 21 October 2003 - 01:31 PM
But then there is the shipping issue. UPS/FEDEX/USPS can turn a perfectly collimated OTA into a misalignment mess. Some fixable, some not. Maybe Orion and others gamble that by accident shippers will knock a Chinese scope INTO alignment occasionally. :o
Posted 21 October 2003 - 03:22 PM
Posted 21 October 2003 - 05:43 PM
It is "easier" for everyone to just let the end user do the testing - sort out the good pieces from the bad. Some retailers like Company 7 (as I understand it) take the time to test each piece and work through any problems before they ship, and TEC, AP, TMB (among others) perform a lot of testing as the manufacturer. Their customers might pay a bit more, and may have to wait a little longer to receive their purchase, but they have better assurance of a good product first time.
I don't mean to sound like the only answer is to pay big bucks for every piece of equipment - that is just not the right answer. There are lots of companies that offer reasonably low prices, and good customer support when something goes wrong. Orion seems to be doing just that in Scott's case. My only point in this trip to the soapbox, is to say that we, the consumer, can help encourage the appropriate level of quality and support in this market. When we shop based only on price or delivery - rather than looking for the best value - we place the folks doing all the testing at a big disadvantage. We can also let others know when a company works us over, or leaves us hanging.
Next time you look at a purchase, do your homework, support the companies that you know are working to do it right. Vote with your dollars and your feet - and run away from the low quality companies with customer dis-service departments.
Posted 21 October 2003 - 06:23 PM
It is unfortunate that is has come to having to send two mounts back. The second, withing 72 hours of delivery. I wouldn't mind paying a few extra dollars to have one work correctly out of the box.
Posted 21 October 2003 - 07:37 PM
Well-said Mike. It is true that products are sold at a targeted price points, and checking every scope would significantly increase labor costs, and therefore equipment costs to the consumer. I’ve been surprised that most of the Chinese scopes I have read about have been of at least descent quality as is. If you get a really good one, they are rated even higher in quality. The first Chinese OTA I used I would have rated as surprisingly good. The OTA I just returned is unfortunately at the opposite end of the spectrum. There is a reason the best companies are more expensive. They would have caught that OTA before it ever made it out the door. Like you said, it’s their attention to detail (read labor costs) that promises better consistency in quality.
With my astronomy budget (read entry level…LOL), I’m always looking for products that provide surprisingly good value for the money, and companies that provide exceptional customer support for the price of their products. (I now consider Orion to be one such company). I fully understand these products will never provide the type of rock-solid quality control the true “giants” offer. But it’s amazing that within each price point there are always a few manufacturers that “raise the bar” in terms of performance/price/value ratios. Some day I hope to own top of the line equipment, but I will be actively searching for just such companies as I work my way toward that lofty goal. In a way, that’s part of the charm this hobby provides. And this excellent forum has done more to educate me over the past few weeks than I could ever have imagined…
Posted 22 October 2003 - 01:13 AM
Hope you end up with a "pick of the litter" scope when this is all done.
Posted 22 October 2003 - 08:26 AM