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A well sorted RC has the edge over big refractors for imaging small DSOs?

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Well, after much further deliberation, and despite still really liking the idea of having a CFF RC, (if only just to look at on cloudy nights), it looks like common sense is going to prevail and we will go with a refractor.

Aperture fever is still raging however, so its looking like an Esprit 150. :icon_biggrin:

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I don't know which is best but I concern myself only with the practice, not the theory. I imaged with Yves' 14 nch ODK for two years and now go after similar targets with a TEC 140. The big one was working at 0.66"PP, the TEC at about 0.9. 

The Barlow question is a good one but Roland Christen would not agree that the Barlow has no place. If you want to blow the standard theory out of the water have a look at this capture by Julian Shaw using a 2x AP advanced barlow at about F15 in a 6 inch refractor. Exposure was about 7 hours from NZ, putting the Sombrero higher than it is for us. Processing was mine and done quickly after a big lunch we had together!

SOMBRERO%20JULIANS%20DATA%20V2%20CROP-X2

My imperfect understanding is that the Barlow was used not to increase the image scale (I think this was resampled downwards to the pre-barlow scale) but to enhance the sampling on the stars and improve their quality. 

There are, in observatories world wide, planty of sexy looking Serrurier truss reflectors gather dust after their owners have been driven to distraction by them. But there are others which do work.

Whatever, I'd have been just a bit pleased with this capture myself!

Olly

Edited by ollypenrice
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I'm in a slightly different dilemma. I have my 8" RC / reducer combo which took a while to fettle, mainly due to getting to grips with RC collimation and now that I've tamed the beast i face a new set of challenges.

  • Keeping the primary mirror clean
  • Keeping the secondary dew free, even with a seconday heater installed.

The RC has a few benefits in that i can image @ 1600mm or at 1100mm with my reducer, but having to keep stripping it down 2-3 times a year to clean the primary is starting to feel like a chore, Whilst my 102mm doublet, is always hassle free and a joy to use.

So for me, I'm thinking that something like a 150mm apo might be the right choice even if the image scale is a little smaller and the resolution is a bit lower vs the RC on galaxies, i think the trade off will be worth it.

Rich.

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1 hour ago, Northernlight said:

I'm in a slightly different dilemma. I have my 8" RC / reducer combo which took a while to fettle, mainly due to getting to grips with RC collimation and now that I've tamed the beast i face a new set of challenges.

  • Keeping the primary mirror clean
  • Keeping the secondary dew free, even with a seconday heater installed.

The RC has a few benefits in that i can image @ 1600mm or at 1100mm with my reducer, but having to keep stripping it down 2-3 times a year to clean the primary is starting to feel like a chore, Whilst my 102mm doublet, is always hassle free and a joy to use.

So for me, I'm thinking that something like a 150mm apo might be the right choice even if the image scale is a little smaller and the resolution is a bit lower vs the RC on galaxies, i think the trade off will be worth it.

Rich.

Why do you need to clean it that often?

Mirror systems don't need to be cleaned that often at all. If you see a bit of dust settle down on mirrors, you don't need to clean it - it will not impact optical performance at all. Most people don't clean mirrors for several years.

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Yup, Decision  is made, I guess if we ever get tired of minimal effort imaging with the Esprit, (as if!) then it could always be traded in for a little used TT RC....

Going to start another thread on the benefits of a temperature compensated auto focuser with a big refractor.

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9 hours ago, Northernlight said:

I'm in a slightly different dilemma. I have my 8" RC / reducer combo which took a while to fettle, mainly due to getting to grips with RC collimation and now that I've tamed the beast i face a new set of challenges.

  • Keeping the primary mirror clean
  • Keeping the secondary dew free, even with a seconday heater installed.

The RC has a few benefits in that i can image @ 1600mm or at 1100mm with my reducer, but having to keep stripping it down 2-3 times a year to clean the primary is starting to feel like a chore, Whilst my 102mm doublet, is always hassle free and a joy to use.

So for me, I'm thinking that something like a 150mm apo might be the right choice even if the image scale is a little smaller and the resolution is a bit lower vs the RC on galaxies, i think the trade off will be worth it.

Rich.

This was my exact reason for moving from the ODK10 to a refractor. I had it for 2 seasons and we have a pretty terrible time over here with yellow pine pollen in the spring. I knew that one day I was going to have to tackle a mirror clean and there was no way I was up for that..... so I sold the scope before the mirrors got that bad and settled on a 152mm refractor.... heaven!!

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36 minutes ago, swag72 said:

This was my exact reason for moving from the ODK10 to a refractor. I had it for 2 seasons and we have a pretty terrible time over here with yellow pine pollen in the spring. I knew that one day I was going to have to tackle a mirror clean and there was no way I was up for that..... so I sold the scope before the mirrors got that bad and settled on a 152mm refractor.... heaven!!

An increasingly long list of people I know have done the same...

Olly

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For me, it's a similar issues as Sara with lots of dust and pollen type debris on the mirrors, hence wanting a bigger apo as easy to clean and maintain.

 

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Sadly even second hand this would be way beyond my budget.  My budget will literally extend to a SW esprit 150. 

Edited by Northernlight
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7 hours ago, Northernlight said:

Sadly even second hand this would be way beyond my budget.  My budget will literally extend to a SW esprit 150. 

I don't think that there is a jot wrong with the Esprit 150 - It seems like a well accomplished and perfectly performing scope to me...... One I would have bought had a secondhand TMB 152 not been offered to me :)  Couple with the right camera and you can have some very good resolution imaging (sky allowing of course!)

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10 hours ago, swag72 said:

don't think that there is a jot wrong with the Esprit 150 - It seems like a well accomplished and perfectly performing scope to me.....

Sara, do you not find it noticeably slower than the ODK10? 

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My TMB runs at f7.9....... While one of the reasons for the ODK10 was the speed, If I'm honest I don't notice speed in any way. The subs come in (1800s for NB, 300s for RGB and 600s or 1200s for lum) -Is one faster than the other? Sure on paper.... do I notice it in the real world? Not at all. But then I'm not about to do a comparison as I can't as I have a different camera on the TMB than on the ODK.

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Its a tough call on the old speed debate. If you live in the uk where the weather is usually terrible and clear nights are rare i can understand the obsession over speed.

I used to obsess over speed, but id rather have 10 great subs on slower scope than 20 poor subs on a faster system

Edited by Northernlight
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5 hours ago, gorann said:

Any idea of the asking price for this one?

It looks like the original TOA-150 rather than the -150B (improved focuser only?)

I'd guess at £5-7k, maybe!

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1 hour ago, Northernlight said:

Its a tough call on the old speed debate. If you live in the uk where the weather is usually terrible and clear nights are rare i can understand the obsession over speed.

Yes, that's the point.

1 hour ago, Northernlight said:

I used to obsess over speed, but id rather have 10 great subs on slower scope than 20 poor subs on a faster system

...as is this one!

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