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Equipment Discussions >> Reflectors

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dscarpa
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Reged: 03/15/08

Loc: San Diego Ca.
Switching from SIPS to Paracorr 2.
      #5826601 - 04/27/13 03:53 PM

I was going to get SIPS on my 11" F/5 Teeter STS with Zambuto optic but after concerns with barlowing decided a Paracorr 2 would suit me best. It turns out that SIPS can only be used with a barlow that's parfocal with the eyepiece used in it. For me that works out to a grand total of one A team eyepiece with 5 barlows which is far from ideal. With the adjustable Paracorr I should be able to use at least some eyepiece barlow combos that aren't parfocal. I probably wouldn't use the Paracorr when barlowing most of the time and it's much easier to take out than the SIPS. I'll buy from Astronomics so they can get in on my newt action. I bought an excellent passive-laser collimation set on CNC so no sale for them there. As to the newt Rob says we are waiting for the optic with June is still the ETA! David

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ausastronomerModerator
Carpal Tunnel
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Reged: 06/30/03

Loc: Kiama NSW (Australia)
Re: Switching from SIPS to Paracorr 2. new [Re: dscarpa]
      #5827272 - 04/27/13 08:25 PM

I have 3 barlows which I use in all my newtonians, albeit not that often as I only need the barlows on nights of exceptional seeing when I can go 500X plus.

I don't see any need to use the barlow + paracorr in either of my F4.5 scopes having regard to the short focal length eyepieces and the fact the barlow helps EOF performance in any case.

Cheers


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: Switching from SIPS to Paracorr 2. new [Re: dscarpa]
      #5827357 - 04/27/13 09:29 PM

Quote:

I was going to get SIPS on my 11" F/5 Teeter STS with Zambuto optic but after concerns with barlowing decided a Paracorr 2 would suit me best. It turns out that SIPS can only be used with a barlow that's parfocal with the eyepiece used in it. For me that works out to a grand total of one A team eyepiece with 5 barlows which is far from ideal. With the adjustable Paracorr I should be able to use at least some eyepiece barlow combos that aren't parfocal. I probably wouldn't use the Paracorr when barlowing most of the time and it's much easier to take out than the SIPS. I'll buy from Astronomics so they can get in on my newt action. I bought an excellent passive-laser collimation set on CNC so no sale for them there. As to the newt Rob says we are waiting for the optic with June is still the ETA! David



You misunderstood what "SIPS can only be used with a barlow that's parfocal with the eyepiece used in it" meant.
My PowerMate, when inserted, requires no refocusing because the height of the body is equal exactly to the necessary "pull-back" for the eyepiece.
With that kind of barlow, any eyepiece used in it will require no change in focuser position.
That means any eyepiece can be used so long as the barlow doesn't require any additional infocusing or outfocusing.
Your eyepieces don't have to be parfocal, the barlow has to be parfocal with the eyepiece inserted into it.
You do have to be careful how far in your eyepiece focuses, but so long as that isn't a problem, the barlow isn't a problem but only if it requires no refocusing.
Basically, the SIPS has the Paracorr lens in the correct position in the focal cone so that eyepieces can be moved in and out using the focuser to place the eyepiece focal plane the correct distance from the lens. A PowerMate moves the focal plane back a bit so the eyepiece is positioned exactly the height of the Powermate farther back.
Any barlow that moves the focal plane differently will defeat the purpose of setting the eyepiece-to-lens distance.
There may be other barlows that are similar (Siebert? Explore Scientific? Others?) but that's how I understand it.


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Switching from SIPS to Paracorr 2. new [Re: Starman1]
      #5827553 - 04/28/13 12:10 AM

Quote:

You misunderstood what "SIPS can only be used with a barlow that's parfocal with the eyepiece used in it" meant.




So here's a question for you Don:

If one thinks of a Barlow and an eyepiece as a new, unique eyepiece, why is it that you can't just focus it as you would any other eyepiece?

Jon


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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Switching from SIPS to Paracorr 2. new [Re: Jon Isaacs]
      #5827636 - 04/28/13 01:27 AM

Jon,
I don't know.
I'll have to ask and report back.


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johnnyha
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Reged: 11/12/06

Loc: Sherman Oaks, CA
Re: Switching from SIPS to Paracorr 2. new [Re: Starman1]
      #5827885 - 04/28/13 08:38 AM

Good call. I think the SIPS is extreme overkill for an 11" f5 STS tube dob. It seems like more of a solution for 20"+, f4 and faster dobs.

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dscarpa
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Reged: 03/15/08

Loc: San Diego Ca.
Re: Switching from SIPS to Paracorr 2. new [Re: dscarpa]
      #5828294 - 04/28/13 01:01 PM

My XWs and for that matter every A eyepiece but my 12 Delos aren't parfocal in the 1.25" TV barlows and Powermates. Being able to remove the Paracorr without having to do the same with a $500 FT focuser makes the whole choice moot. An Ethos in a Powermate in a Paracorr for a grand total of 16 elements is a bit much even for me! Not to mention the stack would look like a snail's eye. I'm still getting the FT. David

Edited by dscarpa (04/28/13 01:08 PM)


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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Switching from SIPS to Paracorr 2. new [Re: Jon Isaacs]
      #5829915 - 04/29/13 11:00 AM

Quote:

Quote:

You misunderstood what "SIPS can only be used with a barlow that's parfocal with the eyepiece used in it" meant.




So here's a question for you Don:

If one thinks of a Barlow and an eyepiece as a new, unique eyepiece, why is it that you can't just focus it as you would any other eyepiece?

Jon



Well, having spoken to TeleVue about it:
The SIPS Paracorr lens is placed in a specific place in the light cone of the telescope. Once that is dialed in, what happens after that, you are correct, doesn't matter, where barlows are concerned.
Though it is possible that some older, very long, barlows might protrude hazardously far into the focuser, so long as the barlow doesn't impact the lens, there is no problem with using any barlow with the SIPS.
2" Barlows cannot hit the lens, and 1.25" barlows will automatically be pulled back by the 1.25" adapter in the focuser. Drop-In adapters wouldn't be recommended, obviously.

It's also possible that certain standard barlow+eyepiece combinations might run out of focuser travel due to inward focuser movement, but this might be true without the SIPS lens, too.

Having a barlow that is parfocal with the eyepiece is a convenience, but not required.

Jon, your question was spot-on, and a good one. Thanks.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Switching from SIPS to Paracorr 2. new [Re: Starman1]
      #5829954 - 04/29/13 11:21 AM

Quote:

Quote:

Quote:

You misunderstood what "SIPS can only be used with a barlow that's parfocal with the eyepiece used in it" meant.




So here's a question for you Don:

If one thinks of a Barlow and an eyepiece as a new, unique eyepiece, why is it that you can't just focus it as you would any other eyepiece?

Jon



Well, having spoken to TeleVue about it:
The SIPS Paracorr lens is placed in a specific place in the light cone of the telescope. Once that is dialed in, what happens after that, you are correct, doesn't matter, where barlows are concerned.
Though it is possible that some older, very long, barlows might protrude hazardously far into the focuser, so long as the barlow doesn't impact the lens, there is no problem with using any barlow with the SIPS.
2" Barlows cannot hit the lens, and 1.25" barlows will automatically be pulled back by the 1.25" adapter in the focuser. Drop-In adapters wouldn't be recommended, obviously.

It's also possible that certain standard barlow+eyepiece combinations might run out of focuser travel due to inward focuser movement, but this might be true without the SIPS lens, too.

Having a barlow that is parfocal with the eyepiece is a convenience, but not required.

Jon, your question was spot-on, and a good one. Thanks.




Don:

Thank you for taking the time to clarify the issue. My understanding was that the SIPS made the individual characteristics of the eyepiece irrelevant. It is essentially the same as positioning the Paracorr properly and then only using the Tuneable Top for focusing.

Not every Barlow will come to focus within the range of the SIPS and some of those long older barlows may contact that Paracorr, that would be bad, but other than that, it did seem to me that any Barlow should work.

As an aside concerning Barlows. I have a few of those older, long Barlows, mostly Meades from the 1980s... I never use them, it seems like they would either hit the diagonal of a refractor/sct or the Paracorr...

Jon


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dscarpa
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Reged: 03/15/08

Loc: San Diego Ca.
Re: Switching from SIPS to Paracorr 2. new [Re: dscarpa]
      #5830414 - 04/29/13 02:46 PM

Thanks for checking that out Don! Might as well go back to SIPS. Called TV about a week ago but the person I talked to couldn't give me a green light on using non parfocal eyepiece barlow combos so I canceled SIPS. At F/5 I could get by without a coma corrector but the refractor like image with is just too sweet to pass up. David

Edited by dscarpa (04/29/13 09:55 PM)


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JMW
Pooh-Bah


Reged: 02/11/07

Loc: Nevada
Re: Switching from SIPS to Paracorr 2. new [Re: dscarpa]
      #5833394 - 04/30/13 10:51 PM

I don't use Barlows except for planetary imaging on my SCT. I plan on getting Feathertouch with SIPS on the dob I want to purchase. It appears that the upsides are pretty awesome. Keeping the focuser/eyepiece profile closer to the focuser board and not having to adjust the setting between eyepieces. The only downside is temp removal of the SIPS when collimating.

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dscarpa
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Reged: 03/15/08

Loc: San Diego Ca.
Re: Switching from SIPS to Paracorr 2. new [Re: dscarpa]
      #5834013 - 05/01/13 10:24 AM

As to revoving SIPS check out the review in Astromart. Rob Teeter uses the same system using 5 thumb screws to remove the focuser and the coma corrector. I called him the other day to tell him I did want SIPS after all just before he sent it back to FT. David

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