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Northernlight

Torn between 6" Apo & 10" Newt

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On 16/04/2019 at 22:21, FaDG said:

You're right @alexbb and @Northernlight, if the OTA is not rotated the reference is kept as the image is rotated back in the calibration process.

Apparently at least once the tube rings were not tight enough and the scope rotated a bit while mounting/dismounting without me noticing it. 

Sorry for the mistake.

I was about to post about this must be wrong - but just realised it isn't!

Thanks guys; that's been worrying me for a while!  One more "problem" that I just learned I don't need to solve :).

Billy

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Is this on a permanent set up?  If so collimation should be less of an issue as it should not have to do it very often once set (assuming a stable set up).  If you are intending to strip down every night or go to a dark site then refractor will be the way to go because at F4 you will need to collimate a lot more often.  An F5 system will be more forgiving.

If you ever want to do photometry then the larger aperture will help.

If you ever want to use it for visual then the larger aperture will help.

Reflectors have much less issues with regards colour correction given a decent corrector.

Reflectors need a bath once in a while! 

The larger aperture at the same pixel scale will allow you to collect more data in the reflector in the same time (helpful in cloudy UK)

A faster focal ratio means your focus position is more critical - your focuser needs to be more precise.

Diffraction spikes can be a negative for some.

Reflectors can have tube currents (most higher quality ones have oversized tubes/fans to mitigate this).

Reflectors are more bulky and more prone to wind (less of an issue if in an observatory and shielded.

If you continue with a reflector option it might be worth looking at JTW Astronomy.  They make custom reflectors and build to your specs (backfocus, focuser etc).

Ian

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Hi Ian,

I looked at the JTW scopes, but they are too much of an unknown, and without wanting to sound negative, I get the Impression that Mark from its gets easily distracted with other projects, so not sure how long he would take to build the scope.

His scopes do however look like an interesting design. I don't think I would buy one unless it was a special introductory offer.

 

 

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1 hour ago, Northernlight said:

Hi Ian,

I looked at the JTW scopes, but they are too much of an unknown, and without wanting to sound negative, I get the Impression that Mark from its gets easily distracted with other projects, so not sure how long he would take to build the scope.

His scopes do however look like an interesting design. I don't think I would buy one unless it was a special introductory offer. 

 

 

I'd agree that they are relatively unknown in the astroimaging world.  However, they do make quite a bit for the more professional community of which they have more telescopes out there (e.g. GOTO).  They don't get advertised in the same way...  3-4 months is the quoted time for a Newtonian I believe, 6 months for a CDK or more complex design.

I do appreciate that there is always the risk of the unknown.   

 

 

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 Hopefully when JTW has finished work on their new mount, they might have time to focus on building his telescope brand.

I think the biggest problems with JTW is that they appear to be having an identity crisis. They  don't seem to be sure what type of business they are. Are they an engineering company that makes astro gear on the side or a Telescope company that does engineering on the side ?

But either way, I would like to see them start producing some finely crafted scopes for the general pub!ic. Who knows they could be the next TEC of Europe and speaking to mark he seems passionate about astronomy, so hopefully we'll start to see some of his scopes in the wild in the near future.

Edited by Northernlight
Edit

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On 16/04/2019 at 11:30, ollypenrice said:

Some images from a somewhat smaller refractor (140mm).

https://www.astrobin.com/full/393219/0/

https://www.astrobin.com/full/342334/0/

https://www.astrobin.com/full/347486/B/

I'm not looking for a new scope.

Olly

Except the tec 140 is over twice the price of the TS refractor.

I would go with the refractor though.

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4 hours ago, HunterHarling said:

Except the tec 140 is over twice the price of the TS refractor.

I would go with the refractor though.

It is, but the SW wasn't on the market when I bought the TEC (second hand for about the same as the current Esprit 150. ) I don't think there would be much difference between TEC140 and SW Esprit 150 images.

Olly

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On 17/04/2019 at 10:59, alan potts said:

I would go for the refractor but don't be worried by F4 collimation with a Hotech SCA Laser it is very easy. My Dob is F 4.3 which is near and that is only ever 2-3 minutes work.

Nail & Head Alan. Its very clear your happiness will be with a Refractor. I would indeed research a CF model though to save your back!.

For Me I like both. I personally love collimating my scope, its something that's once learnt & mastered is a true part of Astronomy. I wil tweak collimate my Newt twice through an observing session. Nothing to fear

Best Rob

Edited by Rob

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Oh and just to add to the scope choice of the budget you have. I feel the Esprit 120 would be a nice fit. Or the fact that you have a nice collimating tool how about a RASA?!.. I'm sure the collimating skills you hold for the RC would serve you well (caught you post and US replies on CN)

Clear Skies & Good luck. Rob

Edited by Rob
typo

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Collimation isn't the issue with a newt, it is coma removal and the larger your camera chip the harder it gets.  Spacing with the coma corrector is critical and doesn't always resolve the issue.  If you have a decent mount a SW maknewt would be a brilliant alternative and would save you a lot of money - no coma, no diffraction spikes, a flat field f5.3 all faff free.  I bought mine years ago and rate it as the best astro purchase I've ever made (and I've made an awful lot!).

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On 16/04/2019 at 19:30, ollypenrice said:

Some images from a somewhat smaller refractor (140mm).

https://www.astrobin.com/full/393219/0/

https://www.astrobin.com/full/342334/0/

https://www.astrobin.com/full/347486/B/

I'm not looking for a new scope.

Olly

There are other factors at play here Olly, a true dark sky, lots of clear nights, dedication and experience.  I reckon you could also produce some seriously good images with a Newt!

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2 minutes ago, MartinB said:

There are other factors at play here Olly, a true dark sky, lots of clear nights, dedication and experience.  I reckon you could also produce some seriously good images with a Newt!

:D I'm really just trying to show that small apertures can work well with small pixels on small targets. Some would have it that the larger aperture is essential but I'm not convinced that it is, certainly not if the upper limit is 10 inches. On the other hand if the Newt goes up to something like 16 or 20 inches and the seeing supports it then the refractor will fall behind.

Olly

 

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56 minutes ago, ollypenrice said:

:D I'm really just trying to show that small apertures can work well with small pixels on small targets. Some would have it that the larger aperture is essential but I'm not convinced that it is, certainly not if the upper limit is 10 inches. On the other hand if the Newt goes up to something like 16 or 20 inches and the seeing supports it then the refractor will fall behind.

Olly

 

It's the light gathering capability of the Newt which is it's advantage.  In a country where it might take 2 or 3 months to gather 10 hours of data that is helpful!  Having said that I think they are an absolute pain for imaging!

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6 minutes ago, MartinB said:

It's the light gathering capability of the Newt which is it's advantage.  In a country where it might take 2 or 3 months to gather 10 hours of data that is helpful!  Having said that I think they are an absolute pain for imaging!

All the more reason not to lose a night to faffing! The perfect solution is to team up with friends:

985620730_DUALTEC140WEB.jpg.9f2d81d2fe5121b723bd6b9c53e0b9f3.jpg

Olly

 

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