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philhilo

1.6 inch flattener?

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Wasn't sure where to put this, but as it seems to be a newbie error then here it is. Decided I wanted a travel OTA and something wider than my 200PDS. Saw a WO Zenithstar 66SD doublet at a good price on ebay and wehay it arrived. Great reviews from a few years back, looks good. Have now discovered it takes 1.25 or 1.6 inch accessories ..... not the 2 inch flattener I ordered from RVO. Research shows they made a 1.6 inch reducer flattener in the early/mid noughties.

I got it for astrophotography, is there a solution, is there a secret source of 1.6 inch flatteners for f5.9 refractors, can I get a 1.25 inch flattener or would a 1.25 inch flattener work with an APS-C sensor on a DSLR? Or am I up a creek and should I stick it back up for sale, lick my wounds and get something more modern. Cheers for any assistance (especially any suitable flatteners!). Phil

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Hi. 

Are you sure it's a 1.6 flattener you need and not a 2 inch flattener? 

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OK, apart from great excitement when I thought ENS (7 miles away) might have THE flattener, but out of stock. The end of the focuser tube is threaded -outside thread dia 50mm, inside 44mm. I thought the flattener was going to slide inside the focuser, does this mean I can remove the nosepiece off the flattener to reveal an appropriate thread? I have tried but nothing happening by hand so far.

20191202_235709.jpg

20191203_001415.jpg

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1 hour ago, david_taurus83 said:

Have you measured the outer thread with a caliper?

No, just a ruler. I see you are Birmingham south, not far from me in Solihull and the joys of JLR and the airport (thus I am awaiting my LPS D2 filter like yours)!

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1 minute ago, philhilo said:

No, just a ruler. I see you are Birmingham south, not far from me in Solihull and the joys of JLR and the airport (thus I am awaiting my LPS D2 filter like yours)!

I find the D2 to be invaluable! I've also got the IDAS NB1 which I've tried out over the weekend. Not processed the images yet but looks promising.

Have you tried emailing FLO or RVO to see if they can help with the flattener?

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The ZenithStar 66SD Manual does say it has a 1.6" focuser and if you want to use 2" accessories you need their adapter. The field flattener for this scope has a 2" nosepiece which is internally threaded with an SCT-type thread which will screw directly onto the ZS66 SD focuser. Picture posted by David Taurus above. :smile:

Alan

Edited by symmetal

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3 hours ago, david_taurus83 said:

I find the D2 to be invaluable! I've also got the IDAS NB1 which I've tried out over the weekend. Not processed the images yet but looks promising.

Have you tried emailing FLO or RVO to see if they can help with the flattener?

Update after talking to RVO (who recommended the flattener for this scope but they cant know everything) they are sending me an adapter which will screw onto the external 'SCA' thread on the end of the focuser tube which will then receive the 2" nosepiece of the flattener. It will arrive tomorrow, after tonights lovely clear skies...… Hopefully this will not put the flattener so far back that I cant focus, fingers crossed.

As for the filters I am slowly being dragged towards filters with the 8+ skies here and a modded DSLR. Most nebula I simply can't image, M42 is it currently. I can just about do 150 sec subs overhead, which in 90 mins had M33 just about peering out of the fog when processing. Role on my filter before I cave in to a cooled astrocam!

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Update part 2. The adapter arrived, the flattener went into it, the moon looked good, but alas not in focus. All parts were screwed together until metal met metal and the moon was nearly in focus, so close.....but only nearly :'-( Back to square one. Guess I will have to wait for an original or find a flattener with a removable nosepiece (or butcher the flattener and adapter somehow to take a cm out of the length).

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Cracking little scopes, always wished I had never sold mine, seem to remember it has an SCT thread but the flattener is like rockin horse doo doo to find!

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1 hour ago, david_taurus83 said:

Was the lens element of the flattener as close to the drawtube as possible?

The nosepiece of the flattener was all the way down inside the adapter and jammed against the threads, the flange on the flattener was now sitting flush on the top of the adapter and the adapter was screwed as far down the threads as it would go -  flush to the back of the OTA. Depressingly I can't see anyway of getting the lens closer to the drawtube, short of taking something off the length of the nosepiece, and something off either the thickness of the ring on the adapter that screws down to hold the adapter or the threads it screws onto - and I don't actually know how much closer the lens needs to be to achieve focus, less than a cm I suspect, it is close but no cigar.

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In a normal circumstance, if you had a 2" focuser say, the flattener would sit where the line is on the shoulder. I'm assuming you cant remove the nosepiece on this and the end of the nosepiece is at the drawtube?

 

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Yes the shoulder is up against the back of the adapter, and the end of the nosepiece is flush with the threads that go onto the SCT thread on the back of the drawtube. I would guess the nosepiece is a standard length and the adapter internal length is the same.

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Out of interest, focuser draw tube is said to be 1.6" - but there is a thread at the end of it that is a bit larger - could it be T2 thread? (1.6" = 40.8mm - add a mm and a bit and you have 42mm that is T2).

Maybe you could use some FF/FR that has T2 connection instead?

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10 minutes ago, philhilo said:

Alas no. Tried and it won't move, and RHO thought it wasn't removable.

Is it the OVL one? Reading reviews where they say it can be removed.

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Quote

Apparently the thread on the drawtube is 'SCT'. Just had a look at SCT and got a link to Astronomy Connect website which has lists of connectors......

….and if the nosepiece does come off then I wonder what is underneath and if there is a connector to the SCT thread? Hmmm....seeing glints of hope (and it does seem to be a keeper of an OTA and fits my travel needs perfectly). Will be applying some extra elbow grease.

Thanks all for the help so far, and see where it goes tomorrow morning as I am still suffering from the 2 good nights last week zzzzzzz……..

 

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Ta-da, the nosepiece came off the OVL flattener (vice + silicon oven glove + filter wrench) to reveal M48 female threads. Studying the RVO catalogue it appears that I can get an SCT female to T male (10mm optical length) then a female T to M48 adapter (0mm optical length). E-mailed RVO to see what they think of this plan. I see that Blue Fireball in the USA do single SCT to M48 adapter so that's a longer time option - many more clear nights with the new OTA leering at me. Here's hoping it all happens before M31 disappears for me. 

Thanks again all.

Phil

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