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Refractor delivered over fence... Possible damage.


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Rather than use a pinhole star test why not use the classic ballbearing method? Glue a ballbearing (EG from a bicycle wheelbearing) onto a black card and prop up a torch to shine on it. Observe this f

Just a word of caution that the further you go with investigation/disassembly you may be weakening your case should you appeal against the delivery company.  Your solar image looks fine, although hard

I'm not sure that all dew shields are a simple push-fit, so it might be worth trying to verify exactly how it does fit before getting medieval on its donkey. Once you're sure, if you can clamp th

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I'm not sure that all dew shields are a simple push-fit, so it might be worth trying to verify exactly how it does fit before getting medieval on its donkey.

Once you're sure, if you can clamp the OTA in place then a pair of marigolds or a rubber strap wrench might allow you to apply a little more controlled force to the dew shield.  Always use the yellow marigolds, by the way.  They look so much more fetching when your other half posts a picture of you to their social media of choice.

James

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The longer 90mm Bressers use a slightly different objective cell design though:

https://stargazerslounge.com/topic/291186-new-bresser-90mm-f133-unboxing-and-initial-thoughts/

Would the AR90 use the same ?

I still think it is likely that the objective will be tilted with the cell having been knocked like that.

With the 127L's the objective cell was metal but the counter cell was plastic as I recall. Same as the Meade AR5's.

Edited by John
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Bresser got back in touch, they said the dew shield is indeed glued on and it needs to be returned so their technical team can fix it. I don't know how as it is glued on. It does look like the lens cell is very bent so I guess I have to. So annoying, if it wasn't glued I could fix it myself. 

 

 

Edited by Shaun_Astro
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1 hour ago, Shaun_Astro said:

Bresser got back in touch, they said the dew shield is indeed glued on and it needs to be returned so their technical team can fix it. I don't know how as it is glued on. It does look like the lens cell is very bent so I guess I have to. So annoying, if it wasn't glued I could fix it myself. 

 

 

The good thing is that as they are the manufacturer, they'll be able to give it the once over and see if it's still in spec.

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Despite the rain I put an artificial star on the pavement about 30m away. Here are the results:

Left vid inside.

Out of focus middle (I couldn't get any diffraction rings to show clearly with the camera (perhaps the torch moved). With 180x I could see them just about, they looked much weaker obviously, but still circular (Doesn't look like I came out of focus enough either).

Focused right vid.

I think the hole in the foil perhaps was too big, despite it being literally pin head sized.

What do you think? I will try on Polaris next clear night. 

 

They look pretty circular to me.

 

2020-10-21-0946_8-CapObj_0000_pipp.avi2020-10-21-0949_1-CapObj_0000_pipp.avi2020-10-21-0951_6-CapObj_0000_pipp.avi

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Looking promising considering the precision of the test, a real star will confirm the exact alignment condition.  At this stage it might be possible to just manually push the tilted component square.  I had a look at my 90mm Bresser today,  The objective cell is effectively separate from the dew shield and secured to the main tube  by 3 screws, these are not adjusters and can be accessed only by removing the dew shield.  Being an entry level telescope, Bresser would appear to have intended a factory set unit with no user adjustments.      🙂

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There does only seem to be one screw on the inside of the lens, which isn't reachable without removing the stuck dew shield.

I was thinking if it's that close to not warent sending it back a bit of a yank might straighten it out. 

I would like to be able to get the lenses out to ensure they are seated properly and not pinched, but I guess this isn't possible. 

For the price I got this for I would rather not hassle bresser too much and risk them chucking it and refunding me. 

IMG_20201021_135726.jpg

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I reckon that little nut and bolt are what is holding the cell / objective / dewshield assembly onto the tube. Sometimes there are three of those at evenly spaced intervals but perhaps they figure that one is enough for the relatively small aperture.

With the dew shield glued into the objective cell it's not going to be possible to get at the other end of that bolt as far as I can see. 

It's not aimed at owner maintenance !

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Yours is very similar indeed to the 90mm F/13 that @Lockie posted pics of in the thread I linked to earlier. This is the same view of the 90mm F/13 and you can see that small nut in the same position. @Lockie did manage to get the dew shield off though - I wonder if he could tell us how ?

 

bres90.jpg

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I have a feeling the lens cell might unscrew using the two gaps in the ring around it. 

I did star test it just now. It's a bit out, not sure what constitutes acceptable though. The included diagonal was pretty bad. Had a good look at Mars and Uranus, some detail in the former. Minimal CA surpsingly.

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I seem to have gotten the dew sheild straight now with some firm pressure, it snapped back into place. Hopefully it's all fixed. I'll try and collimate the focuser better soon. 

 

Here's the sun through it with the supplied solar filter and yellow #8. Notice sunspot 2776.

 

IMG_20201022_123627_782.jpg

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The 1st one involved holding my phone over the eyepiece, so probably wasn't square. This latest one was a dslr at prime focus. Hopefully should be able to star test later and see if the comet shaped stars have gone. 

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Rather than use a pinhole star test why not use the classic ballbearing method? Glue a ballbearing (EG from a bicycle wheelbearing) onto a black card and prop up a torch to shine on it. Observe this from as far away as possible but it will work at 10M. Only light from the bit of the BB closest to the objective will be reflected back towards it so you get an excellent artificial star.

Olly

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Interesting, I don't think I have one lying around though. 

A star test showed a slightly better focused airy disk, the inside focus diffraction rings are very pronounced, but is is more oval now, pinched optics?

The outside focus is still blurry, I can barely see any diffraction rings, sigh.

Here's an unedited cropped image of the moon, prime focus, 1300D, about 34x magnification with a 26mm diag chip, and another edited version. It's very difficult to focus with the DSLR zoomed in with the refractor wobbling about on it's crappy plastic clamshell, and the mirror movement always seems to blur the images slightly.

 

 

 

IMG_0926_Cropped.JPG

 

 

IMG_0926_Mod3.JPG

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From this image it seems the lens is under corrected, it matches what I see (but what I see is significantly worse). What would be ideal thing to do? Send it back? Or is this acceptable, I don't think I can get the lens out let a long reduce spacing.

 

post-59900-14074179068478_thumb.jpg

Edited by Shaun_Astro
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