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Veridian
sage
Reged: 07/17/06
Posts: 478
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Now that I have an ETX-60AT (BB), I am coming up with a lot of questions. I'm not entirely new to refractors (10 so far and multiplying), but I am new to the ETX line. I think this is quite the cool little scope and look forward to having some real fun with it.
Ok,, here goes:
1. How do the thermal qualities of ABS plastic perform in the cold temperatures we get around here in the upper Mid-West? Am I going to easily crack or break something on the scope or tripod?
2. How tight is the objective fitted in the cell (relating to question #1)?
3. Has anyone had any luck collimating one of these scopes using a 'Cheshire Eyepiece'?
$. Does the flex shaft focus knob assembly (described on the Weasner site) work as well on the newer stock focus shaft location as it does on the older models?
6. Do the 60 and 70mm models share the same tube style,, just different lens cells?
This should be enough of a list of questions for now. I have more, but don't want to push my luck. You'll see that I haven't even begun to ask about the drive and 'go-to' Auto-Star system yet. 
Thank you all,
Mark J.D.
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jgraham
Postmaster
Reged: 12/02/04
Posts: 6754
Loc: Dayton, Ohio
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“How do the thermal qualities of ABS plastic perform in the cold temperatures we get around here in the upper Mid-West? Am I going to easily crack or break something on the scope or tripod?”
The glass transition temperature (the temperature where plastic transitions from being soft and pliable to brittle and glass-like) for ABS is typically about 110C, so the difference between summer and winter temperatures shouldn’t matter too much as far as how brittle the material is.
“How tight is the objective fitted in the cell (relating to question #1)?”
I’m not sure. I’ve taken a peek at mine a couple of times and I wouldn’t worry too much cracking due to thermal expansion differences. I bigger problem in cold weather is probably the lubrication of the moving parts; the grease can really thicken up when it gets cold. I’d recommend using a jumpstart battery or an AC/DC adapter.
“Has anyone had any luck collimating one of these scopes using a 'Cheshire Eyepiece'?”
Good question. I haven’t had a noticeable problem with mine as I typically use the visual port for low powers, wide fields, and the camera port for anything requiring precision.
“Does the flex shaft focus knob assembly (described on the Weasner site) work as well on the newer stock focus shaft location as it does on the older models?”
It should work, but the re-designed focuser on the ETX-60/80BB was intended to eliminate the problem that the flex-focus cable solved (the focus knob becoming unreachable between the tines of the fork).
“Do the 60 and 70mm models share the same tube style, just different lens cells?”
The ETX-60/70/80 are nearly identical. The only distinguishing difference in the OTA’s is the redesigned focus knob on the BB models.
--------------------
-John
================================================
Homebuilt scopes from 4.25-16.5"
Meade LXD75-N6/SN6/SC8, DSX-90, ETX-60BB, ETX-125PE, DS-2130
Orion StarBlast, BinoViewers, Coronado PST
Rebel XT/XTi, DSI Pro (I, II, & III), DSI, LPI, Electronic Eyepiece, Phillips SPC900NC
Tasco 60mm Refractors
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Veridian
sage
Reged: 07/17/06
Posts: 478
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Hi John,
Thank you for taking the time to answer all of my questions. Very good information you shared here.
I should have been more clear about what I'm after when asking if the tube design for the 60 is the same as for the 70mm.
It looks as though they could fit a 70mm cell into this 60mm tube. The inside diameter of this tube is 83mm (8.3cm) at the threaded part just ahead of the obj. cell. Was wondering what the 70mm measures at?
Regarding the focuser,, my guess is that it was designed for the earlier model with in-line focus shaft and I was thinking that the focuser accessory described in Weasner's site could get in the way on this newer model. The diameter of the knob on this flex focuser looks larger, which should speed up the focusing and be a little easier to use when wearing gloves. Also, I was hoping for a way to settle down the shakes a bit while focusing and thought this flex shaft focuser would be of help. My main concern is if it will just be in the way though. Maybe someone who has put one on this model will read this and chime in here?
Thanks again, 
Mark J.D.
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David Castillo
scholastic sledgehammer
Reged: 09/09/06
Posts: 881
Loc: Carmel Valley, Ca
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My ETX is a Grab-and-go. No thermal problems exhibited yet. The cell should retain the lens with minimal force: too tight and you'll get distortion. As far as collimation, star tests show it's right on the money. I've plopped a laser in the ep holder and check to see if the mirror has seated at the proper angle after flipping it...it has varied. A flexi-focus knob will isolate vibrations better than the Knob. I believe the OTA is close to the same; I've seen ads for replacement lens covers that the vendor claims fits both 60's and 70's.
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Dave
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Veridian
sage
Reged: 07/17/06
Posts: 478
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" I believe the OTA is close to the same; I've seen ads for replacement lens covers that the vendor claims fits both 60's and 70's."
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Dave
*************
David,
Now, there's the clue! I should have looked on the Meade site to see if the dew shield they sell as an accessory is the same part number for both the 60 and 70mm. Seems that the focal length is the same for each model also.
Thanks,
Mark J.D.
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mike174
sage
Reged: 01/04/05
Posts: 379
Loc: North-Central, NJ
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I picked up a few ETX-70A's and wonder if the USB camera is any good?
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