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Garrett BT70-90 MK II's arrived!

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#26 Jawaid I. Abbasi

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Posted 04 December 2010 - 02:27 PM

Von,
If you have a perfect collimated scope and can not see any effect even in bright day light then I would say that you should keep if you are 99.5% satisfied with the views it provided to you.

I have the big brother APM-100 and I too satisfied 99%. What I care is perfect collimation using different eyepieces and I am very happy at this point.

You may get exchange or refund but if you get about the same or worst then again you will need to send it back. Keep in mind that even with the inspection at GO; you may still get a little miscollimated scope. So, having a perfect collimated binocular is a bless.

From your post; it seems to me that you are quite happy with the performance of your binocular.

#27 Vondragonnoggin

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Posted 04 December 2010 - 02:51 PM

Yeah, the performance is pretty awesome from the little I've tried it so far. It that stupid nagging at the back of my head on a couple minor scratches that doesn't affect performance as far as I can see.

This is a lot of money to me, but small compared to any other BT that accepts standard ep's. In fact, this is the cheapest BT out there to accept standard ep's.

Unfortunately for me, this might be the first mile in a highway headed for Binoviewers and refractor or Kowa Highlanders or some other such apparatus that will knock my socks off with wide angle lower power binocular views.

This one seems like the ultimate grab and go with it's compact size and lower weight.

#28 EdZ

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Posted 04 December 2010 - 02:56 PM

Would you consider these scratches or sleeks.

My Celestron CR150 refractor has many sleeks in the objective lens. It's never really bothered me one bit. No it's not a perfect lens, but also I can't see those sleeks unless I shine a flashlight on it. It was stated correctly above; shining a flashlight on a lens will make your jaw drop.

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#29 Vondragonnoggin

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Posted 04 December 2010 - 03:09 PM

I don't have enough experience to know the difference. They don't clean off with the lens pen, but it does take a certain angle to view them with a flashlight. If I was to shine the flashlight directly over the focuser, they won't show up. I kind of regret using a flashlight to inspect them. No flashlight, they are invisible.

#30 Vondragonnoggin

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Posted 04 December 2010 - 03:11 PM

I have also read that objective lens scratches are less harmful to the view than occular scratches, but these are not really occular scratches either since they are between the EP and the objective.

#31 Vondragonnoggin

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Posted 04 December 2010 - 03:20 PM

I got this definition off the web from an astronomy glossary -

A very fine scratch visible at only certain angles. Sleeks are found during polishing, usually being caused by impurities in the polishing compound or other contaminates. Sleeks also occur when the polishing compound dries out during a polishing session.

Mine appear to be sleeks by this definition, but they are kind of long (3/16, and 1/4 approx)

#32 KennyJ

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Posted 04 December 2010 - 03:33 PM

Personally , I wouldn't lose any sleep over these slight imperfections .

Just ENJOY the views THROUGH the instrument .

Kenny

#33 Joad

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Posted 04 December 2010 - 03:34 PM

I too can be very obsessive about the perfection of a glass surface, but what EdZ and others here are saying is correct: if you are satisfied with the view, and you can't even see the imperfections without doing a flashlight test, you are much better off simply enjoying your binoculars. The hassle of returning them and finding a substitute at this price range that will be just as good as the set you have is simply not worth it. A short time of use will introduce all sorts of little dust spots and such on your objectives that will show up on a flashlight test but won't affect your viewing. Enjoy your binoculars: looks like you got a good set.

#34 Vondragonnoggin

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Posted 04 December 2010 - 03:50 PM

Thanks everyone for the input. I figured as much that I was being too picky. They really are awesome to view through and 90 degree occulars is really comfortable. I will do my best to forget about it and keep that flashlight away. I made the same mistake shining it on my dob mirror. Yikes. I don't do that anymore either. watching guys take a 2 inch spot on a 50 inch mirror and blacking it out saying it doesn't affect the view helps also.

#35 beachchairbill

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Posted 04 December 2010 - 03:51 PM

Von,

Mike and EDZ have said it well and I would not return them if you find that they don't bother your viewing at the night sky or during day time.

I would give them a good solid test with the eps that you will be using most of the time and if their is no distortaion during your day and night viewing, I would keep them. Using the flashlight test has proven to be worthwhile for finding chipped and cracked glass as well as scratches on the coatings of the objective lenses as well as serious cracks and particles floating inside the tubes.

You don't want to go where I have been.

If you enjoy the views you have a keeper. The thing in the back of your mind will be overcome by the wonderful views you will have for a long time to come.

BB

#36 Vondragonnoggin

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Posted 04 December 2010 - 04:01 PM

I tried these with 20mm q70's, 9mm EWA's and the 25x that come with it. All seem great accept for the issue of the compression ring and undercut ep's. I am going to try to find a solution to fix that one on the EP side myself. EWA's and q70's were cheap, but had good performance anyway. Both of those give a nice wide field and the BT has a long enough FL to be a little forgiving on edge performance. If I come up with a good solution on my undercuts, I will share it for sure. the flashlight inspection reassured me on the other areas of the BT. Looking at the insides of the tubes, inside finish being dark and somewhat rough, etc. Just the one lens with the imperfections had me worried.

#37 Jawaid I. Abbasi

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Posted 04 December 2010 - 04:19 PM

Well,
Enjoyed and we are all waiting of your first report and if you able to go at the "DARK" site then you will really love this Baby. :)

#38 GlennLeDrew

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Posted 04 December 2010 - 04:40 PM

Don't worry a jot about those two little sleeks. You have much worse problems in your own eyes! (Not sleeks, but irregularities and such.)

I think BB should refrain from exhorting recipients of new gear to haul out the flashlight and subject their optics to such a super-revealing test. The little (and surprisingly common) flaws so revealed look so much worse than they are and only cause needless hand-wringing. If nothing is seen under normal use or by sighting through the instrument toward a contrasty background scene, worry no more about image-harming defects or grunge.

#39 Vondragonnoggin

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Posted 04 December 2010 - 06:01 PM

Thanks everyone again for reassuring me. I'll stop the hand wringing (thanks Glenn). It helps to hear the experts reassurances. I trust your opinions. It's already not nagging me now. I just tried them again against some darker green palm tree leaves and can find no irregularities in the views. Seems superb. Tried again at 48x. Seems my issue with the undercuts not tightening all the way are on the same focuser with the sleeks. The compression ring when closed completely is just a hair too long to tighten against the undercut o.d. The other one does tighten. My meade qx70 20mm is a non issue as the barrels unscrew and there is no lens in that section, so you can turn them right around and eliminate the undercut section by having it at the bottom of the focuser, rather than the top.

The 9mm EWA's cannot be turned around. They have a lens element in that section and the barrels don't screw in far enough turned around to have contact with the compression ring. If the right focuser ring had about 1 more mm space, it could tighten on the undercut.

Does anyone tape their undercuts with electrical tape or similar to pad it so it will tighten properly?

#40 KennyJ

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Posted 04 December 2010 - 06:19 PM

Eric ,

With all due respect , and genuine appreciation and understanding of your natural enthusiasm , I would have thought that 48x magnification coupled with 70mm objectives ( if they really are 70mm ) may just be pushing things a little with binoculars !

Just a friendly thought !

Kenny

#41 Joad

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Posted 04 December 2010 - 06:24 PM

And a good one. Those of us with 100mm BTs find that 48-60X is the highest optimal range. We can go higher (some of us have gone a lot higher), but the performance starts to become problematic.

#42 Vondragonnoggin

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Posted 04 December 2010 - 06:35 PM

I'll keep that in mind too. I tried at 48x after reading Peter's review of these where he used the same type expanse clones for testing at 48x. I am looking for a 12mm to give me around 36x, but not any with 60 degree FOV and long eye relief for what I want to spend. I did find some 12.5 astro tech planetary type with 20mm eye relief and 55 degree FOV for a good price. That would give me a 35x ep. I already have 25x and 22x and am going to try a 28mm for a 16x and I'll have all my magnifications covered.

I thought they performed well last night at 48x on M42 and could see clean separation in the trapezium stars, although it was a little dark compared to my 8" dob, but understandably so.

Wouldn't I be able to spot collimation issues and defects better at 48x over just the using the included 25x?

I was figuring that imperfections and mechanical defects would pop out better, but have not really seen any other than my issue with the compression ring and undercut.

#43 Joad

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Posted 04 December 2010 - 06:42 PM

Precise collimation definitely becomes more important as you increase magnification. The higher you go, the less tolerant collimation imperfections will be.

#44 KennyJ

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Posted 04 December 2010 - 06:47 PM

Eric ,

My previous post to you had a soft , friendly tone , but your response indicates hints of single - mindedness , so I'll respond in like fashion !

Why are you going out of your way looking for DEFECTS and IMPERFECTIONS ???

Kenny

#45 EdZ

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Posted 04 December 2010 - 06:51 PM

Precise collimation definitely becomes more important as you increase magnification. The higher you go, the less tolerant collimation imperfections will be.


I agree.

Have you looked at the Astro Tech Paradigm 12mm. I have pairs of the 18s, 15s and 12s. The 12 is the best of the lot. It's actuially 58°. Very well corrected across the field of view. Eye relief allows me to twist the eyecup out slightly even with my glasses on.

edz

#46 Vondragonnoggin

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Posted 04 December 2010 - 06:59 PM

I will check those out. I definitely like viewing with my glasses on and Kenny, I will STOP looking for IMPERFECTIONS! They're new, and my most expensive piece of astro gear, so just making sure I'm getting the real deal.
:grin:

#47 Vondragonnoggin

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Posted 04 December 2010 - 07:33 PM

Thanks again everyone and looks like only partly cloudy tonight, so I'll try my 20mm and 17.5mm EP's. I'm new and still a little hung up on magnification, but better than last year and at least I got reverse aperture fever and went smaller than my 8" dob and 25x100's this time. I do realize the beauty of low power sweeping and cluster hunting, close/bright dso's. that's why I wanted the BT70's in the first place.

#48 GamesForOne

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Posted 04 December 2010 - 08:05 PM

Seems my issue with the undercuts not tightening all the way are on the same focuser with the sleeks. The compression ring when closed completely is just a hair too long to tighten against the undercut o.d. The other one does tighten.


Hmm, perhaps it would be possible to disassemble the focuser turret and cut the length of the compression ring a bit more? Perhaps GO could advise you on that issue -- and ensure that you do not invalidate any warranty by doing so, or even provide you with a replacement ring that is already precut for you to install.

You can try tape and such in the undercut but I am not a big fan of that solution because 1) the tape may eventually degrade and leave sticky residue all over and 2) you are taking a precisely machined barrel and changing it with an imprecise tape job. If the tape doesn't center the barrel, then you may still suffer merging issues at high power.

From what I recall those Expanse clones have very deep undercuts. Frankly that is the problem!

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#49 daniel_h

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Posted 04 December 2010 - 08:58 PM

r u having trouble tightening the undercuts on the ep's? if so there was a thread in the ep fourm a while ago & members were buying some rubber tape form auto dealers, cutting it to the fit the undercut & sticking it in -problem solved

#50 beachchairbill

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Posted 05 December 2010 - 01:59 AM

I would stay away from opening the focuser turret as you might find another rusty screw. Call Zach and see what he has to say.

BB


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