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First light - FC76DC


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I've used my binoviewer with my 76DCU which also has a FTF2025BCR. It won't work without a Barlow but there's no problem getting it to work with one. I use a Baader 32mm T2 prism though with a 2" nosepiece and a 1.25" T2 ClickLock adapter, and it seems that the prism has an 11mm shorter optical path (not including attachments) than the BBHS T2 mirror diagonal.

If I want to use that prism in cyclops mode then I've got a 50mm extension which I need to add otherwise my eyepieces won't come to focus.

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1 hour ago, Andrew_B said:

I've used my binoviewer with my 76DCU which also has a FTF2025BCR. It won't work without a Barlow but there's no problem getting it to work with one. I use a Baader 32mm T2 prism though with a 2" nosepiece and a 1.25" T2 ClickLock adapter, and it seems that the prism has an 11mm shorter optical path (not including attachments) than the BBHS T2 mirror diagonal.

If I want to use that prism in cyclops mode then I've got a 50mm extension which I need to add otherwise my eyepieces won't come to focus.

Thanks Andrew. I’ve only given it a quick go and that was with the BBHS mirror, so I’ll try my T2 prism and see how I get on. I’ve also only tried it in Q mode, not DCU although I assumed the Q would push the focal point out a bit and help get to focus?

I can also attach the binoviewer directly to the prism if needed.

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Good point Stu about the extender changing the back focus. I haven't used that combination with my binoviewer or been able to find any figures for the DCU with the extender, but when it's used with the FS-60CB it shortens the metal back focus distance by 3.6mm so perhaps something similar is going on with the FC-76.

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Congratulations on getting such a wonderful little scope. There’s just something lovely about the FC76 DCU isn’t there!

Mine has done some local-ish travel but whenever I read about truly dark skies or the wonders of the southern skies, I am very glad that I will be able to bring the FC76 if I am lucky enough to travel to these places!

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Started off tonight’s session with the 17.5mm Morpheus but every star seemed to show a tail, either coma or astigmatism which I’ve never seen before, it was horrendous around higher mag stars. Gave the scope 5-10 to acclimate and the result was like chalk and cheese. Was a bit worried for a moment that the Tak & Morpheus aren’t a particularly good combo. Spending time viewing the targets of Orion soon put those worries to bed, marvellous. The A-D stars of the Trapezium cluster showing very clearly at 32x. Loved the doubles of Nair al Saif & Mintaka too, have a soft spot for faint companion stars.

 

 

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4 hours ago, Andrew_B said:

Good point Stu about the extender changing the back focus. I haven't used that combination with my binoviewer or been able to find any figures for the DCU with the extender, but when it's used with the FS-60CB it shortens the metal back focus distance by 3.6mm so perhaps something similar is going on with the FC-76.

Thanks for that confirmation 👍

I’ve noted that when I use the extender on my FS-60CB, there is very little remaining in focus when using my Pentax XWs. They do come to focus, but only a couple of mm remaining 🤔

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