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Renew interest in TeleVue 1.25" Parracor

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#1 Carlos_Padron

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Posted 24 October 2021 - 12:29 PM

IMG 20210927 171224715 HDR

Hi everyone,

 

I really want to own a TV coma corrector (parracor) for my  Orion Starblast 4.5 which is my preferred scope for fast grab and go observing (pictured here). Being a father of a 6 month old, and a 3 year old, I don't have alot of time to observe with my larger 100mm APO f9 refractor or 10" Dob.

 

I'd be very much interested in a new TV coma corrector for this little scope and I bet others may be as well. I know these didn't sell all that much well in the past but I know of a few people who have this Starblast and enjoy their 1.25 parracor. Will all the rush of people into this hobby due to the pandemic (myself included) there maybe renewed interest.

 

P.S. that 2x4 tripod I made is a great upgrade, totally recommend. Just picked up a 5mm Nagler for this Starblast to upgrade my 5.5mm Meade 5000 UWA and the Nagler is king smile.gif

 

Carlos


Edited by Carlos_Padron, 24 October 2021 - 12:46 PM.

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#2 Augustus

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Posted 24 October 2021 - 12:34 PM

A $300+ accessory that only is really needed with telescopes that usually cost less than that themselves is never going to have a big enough market

Edited by Augustus, 24 October 2021 - 12:34 PM.

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#3 RLK1

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Posted 24 October 2021 - 12:47 PM

What Augustus said although you may be able to find one on the used market from time to time. Sold mine on the astromart years ago. Try using a barlow with your longer focal length eyepieces and it may help clean up the edges, too.


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#4 Carlos_Padron

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Posted 24 October 2021 - 12:48 PM

It doesn't have to cost that much... Others have custom run it for $149. To me that tells me it's possible. Seibert Optics being one of them.

 

I also use TV eyepieces which cost more than this scope so 300 isn't a deal breaker. There's a need and if we can have a limited run I'd be one to jump on it. It's been a minute.

 

Carlos


Edited by Carlos_Padron, 24 October 2021 - 12:56 PM.


#5 RLK1

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Posted 24 October 2021 - 12:55 PM

It doesn't have to cost that much... Others have custom run it for $149. To me that tells me it's possible. 

Really?, from who? I'd sure like to know where the lens is being sourced from and it wouldn't surprise me if it turned out to be a low power multi-element barlow.



#6 Carlos_Padron

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Posted 24 October 2021 - 12:57 PM

https://www.siebertoptics.com/


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#7 SteveG

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Posted 24 October 2021 - 01:17 PM

The solution for me was to buy a used LVW22 for low power. It's 65 deg afov shows little to no coma in my f5 scopes. 


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#8 havasman

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Posted 24 October 2021 - 01:23 PM

If you've just got to have a coma corrector for that scope you're more likely to get satisfaction by changing the focuser to a 2" or buying from Siebert if you think he's got what you need. Televue don't do minor short term runs but supply in volumes that generate ongoing profits. And $149 as a price point is just fantasy. They would spread R&D, tooling, packaging, marketing, supply chain management, etc. across a VERY small number of projected sales units and arrive at a $$$$ price. They'd probably want substantial deposits w/o guarantee of delivery. I'd bet against it ever coming about. The market is minuscule. 


Edited by havasman, 24 October 2021 - 01:28 PM.

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#9 RLK1

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Posted 24 October 2021 - 01:36 PM

The solution for me was to buy a used LVW22 for low power. It's 65 deg afov shows little to no coma in my f5 scopes. 

While it's nice to know it works for you, the scope in question is an F4 and having a 4.5" f4, I know it's loaded with coma. 


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#10 SteveG

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Posted 24 October 2021 - 01:53 PM

While it's nice to know it works for you, the scope in question is an F4 and having a 4.5" f4, I know it's loaded with coma. 

Yep - I'm aware. I think the OP would be better off buying a similar small scope that is f5.


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#11 CrazyPanda

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Posted 24 October 2021 - 02:34 PM

These darn scopes are so illogical.

 

1. It's borderline criminal that scopes this small come as F/4 instruments. There's no need for it. At a MINIMUM it should be F/5. That would have such negligible consequences to its size and weight I cannot fathom why it would be F/4.

 

2. Look at that tripod/table that the scope has to sit on to be stable at a reasonable viewing height. That totally defeats the purpose of such a small scope in the first place.


Edited by CrazyPanda, 24 October 2021 - 02:38 PM.

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#12 Jon Isaacs

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Posted 24 October 2021 - 11:10 PM

 It's borderline criminal that scopes this small come as F/4 instruments. There's no need for it. At a MINIMUM it should be F/5. That would have such negligible consequences to its size and weight I cannot fathom why it would be F/4.

 

 

I've said for as long as these scopes have been available, they should have been F/5 rather than F/4.

 

Nonetheless, a 4.5 inch F/4 Newtonian has a coma free, diffraction limited field of 0.18°, a 6 inch F/5 has a coma free diameter of 0.21°, not much larger. 

 

Jon



#13 CrazyPanda

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Posted 24 October 2021 - 11:24 PM

The coma-free field is only part of the story though. 

 

If coma increases by the cube as focal ratio decreases, then we should expect the edges of a given eyepieceto show comatic stars that are (5/4)^3 = ~2x the size in the F/4 scope as in the F/5 scope.

 

The whole field is simply going to look a lot worse in an F/4 scope than an F/5 scope.



#14 Jon Isaacs

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Posted 25 October 2021 - 01:14 AM

The coma-free field is only part of the story though. 

 

If coma increases by the cube as focal ratio decreases, then we should expect the edges of a given eyepieceto show comatic stars that are (5/4)^3 = ~2x the size in the F/4 scope as in the F/5 scope.

 

The whole field is simply going to look a lot worse in an F/4 scope than an F/5 scope.

 

The coma is proportional to the coma free field.  My point is this:  In a small scope, don't get all bent out of shape about coma.  Coma is a big issue in a 12.5 inch F/4.06, stars are brighter by a factor of about 8, coma is brighter.  In a smaller scope, things are just not as obvious.. 

 

Viewing the planets, magnifications are not going to be all that different so the coma free field is important.  

 

Jon


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#15 Starman1

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Posted 25 October 2021 - 04:27 PM

 

 

Hi everyone,

 

I really want to own a TV coma corrector (parracor) for my  Orion Starblast 4.5 which is my preferred scope for fast grab and go observing (pictured here). Being a father of a 6 month old, and a 3 year old, I don't have alot of time to observe with my larger 100mm APO f9 refractor or 10" Dob.

 

I'd be very much interested in a new TV coma corrector for this little scope and I bet others may be as well. I know these didn't sell all that much well in the past but I know of a few people who have this Starblast and enjoy their 1.25 parracor. Will all the rush of people into this hobby due to the pandemic (myself included) there maybe renewed interest.

 

P.S. that 2x4 tripod I made is a great upgrade, totally recommend. Just picked up a 5mm Nagler for this Starblast to upgrade my 5.5mm Meade 5000 UWA and the Nagler is king smile.gif

 

Carlos

 

You can make your own with some ingenuity:

https://www.cloudyni...coma-corrector/


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