My own cure for an aTak of quality fever

[Moonshane]

I have recently been reading all the threads about wonderful fracs and wondering how on earth I was going to ever fund one. I have two really great ed fracs (120ed skywatcher and 102mm Astro Tech ed) but you know how it is when we have cloudy nights...........

This week for the first time,  I have got around to putting my replacement 6" f11 newt on my eq5 with binoviewers for a look at Jupiter. In mediocre seeing the view was stupendous, no doubt aided by the 1/10 optics and bvs/tracking mount. I even managed a decent image at 272x.  The effect of the gpc 1.7x is that focal length Is 2720mm allowing a minimum magnification of 108x,  a great range for lunar and planetary.  I have high hopes for this season. The comfort and convenience of this setup is a real boon and all desire for an expensive frac has dissipated for the time being.  For £160 used plus £75 for the rings (used) this is a truly excellent scope. The fact I can focus with binoviewers is a big bonus.

[Ibbo!]

Its certainly one way of doing it

I have an 8" mirror that is about f13 but is very awkward at that length and a the figure is not great.

If i could get it refigured down to about f9/10 it would be more managable, I think.

One day I might get it done if I can get somebody to do it for me at a resonable price.

[Moonshane]

Go for it buddy.  They do take a little effort but it's lighter than my 120ed and the views amazing. To be fair though the 120 is pretty impressive too.

[Moonshane]

Ps John Nichol might be able to sort it?

[jetstream]

4 hours ago, Moonshane said:

In mediocre seeing the view was stupendous, no doubt aided by the 1/10 optics

They call these 150mm f11 newts "refractor killers" and with good reason IMHO.Truly APO chromatic, next to zero coma and that nice central obstruction allows a great maintaining of the MTF for those fine lunar/ planetary details that no smaller aperture could show obstructionless.

The f11 will also allow most eyepieces to perform with their near best spot size as well...the beamsplitter will control Jupiters brightness ...

And now we add bincular summation to the picture... Great set up Shane.

 

ps what size secondary does it use?

Edited April 23, 2017 by jetstream

[nightfisher]

Very nice set up, looks like you have t set up well for a tall person to just stand with ep at eye level

[niallk]

Very nice indeed!

Out of interest, how do the views through the binos compare in the 6" f11 vs your faster/larger dobs?

[Chris]

It's an impressive thing on the outside before you even get the to views, and I think I get a hint of how good this 6" f/11 must be from my Synta 6" f/8.

Literally the only thing I don't like is the four faint wide diff spikes coming off bright planets with Newt's, for some reason they really irritate me. I do like to see a clean disc when viewing plants.

How are the diffraction spikes on your f/11, Shane? any faint wide spikes when viewing Jupiter? Having said this, I guess spikes are a small price to pay when you consider the money saved over a 5-6" Apo!

Another cheap alternative is the classic long crown and flint frac around f/11-15, but must confess the focuser is at a better end of the tube for your back with the long Newt  

I'm currently grinding a 8.75" f/6.7 which should be interesting on planets if I can get a good figure on it...still a long way to go with that though!

[Stu]

Glad the scope is working out well Shane. I wasn't able to put the time in to get best use out of it but it's in a good place now  

[RobertI]

@Moonshane that's a lovely piece of kit, would love to have a look through that. Did the EQ5 handle it ok (guess it must have!)? It doesnt look like Orion Optics make this scope anymore so a nice scope have bagged. 

 

3 hours ago, jetstream said:

that nice central obstruction allows a great maintaining of the MTF for those fine lunar/ planetary details that no smaller aperture could show obstructionless.

Sorry @jetstream what is MTF?

30 minutes ago, Chris Lock said:

I do like to see a clean disc when viewing plants.

If you are seeing spikes Chris, I think I know where you are going wrong! 

Edited April 23, 2017 by RobertI

[nightfisher]

33 minutes ago, Chris Lock said:

It's an impressive thing on the outside before you even get the to views, and I think I get a hint of how good this 6" f/11 must be from my Synta 6" f/8.

Literally the only thing I don't like is the four faint wide diff spikes coming off bright planets with Newt's, for some reason they really irritate me. I do like to see a clean disc when viewing plants.

How are the diffraction spikes on your f/11, Shane? any faint wide spikes when viewing Jupiter? Having said this, I guess spikes are a small price to pay when you consider the money saved over a 5-6" Apo!

Another cheap alternative is the classic long crown and flint frac around f/11-15, but must confess the focuser is at a better end of the tube for your back with the long Newt  

I'm currently grinding a 8.75" f/6.7 which should be interesting on planets if I can get a good figure on it...still a long way to go with that though!

And of course another way to get a large Apo cheap is a Maksutov, with the benefit of being able to use bino viewer with no mods

[Moonshane]

4 hours ago, nightfisher said:

Very nice set up, looks like you have t set up well for a tall person to just stand with ep at eye level

5 hours ago, jetstream said:

ps what size secondary does it use?

I sit mainly Jules

Secondary is under one inch so pretty small albeit not too specialist.

[Moonshane]

2 hours ago, nightfisher said:

And of course another way to get a large Apo cheap is a Maksutov, with the benefit of being able to use bino viewer with no mods

Very true Jules although no mods required for any of my scopes for bvs

[Moonshane]

4 hours ago, niallk said:

Very nice indeed!

Out of interest, how do the views through the binos compare in the 6" f11 vs your faster/larger dobs?

Not tried in earnest yet but will do soon enough :0)

[Moonshane]

3 hours ago, Chris Lock said:

It's an impressive thing on the outside before you even get the to views, and I think I get a hint of how good this 6" f/11 must be from my Synta 6" f/8.

Literally the only thing I don't like is the four faint wide diff spikes coming off bright planets with Newt's, for some reason they really irritate me. I do like to see a clean disc when viewing plants.

How are the diffraction spikes on your f/11, Shane? any faint wide spikes when viewing Jupiter? Having said this, I guess spikes are a small price to pay when you consider the money saved over a 5-6" Apo!

 

I don't view many plants lol. The spikes are there bit I learn to ignore them. I tried a curved spider but found I preferred the standard four straight vanes.

2 hours ago, RobertI said:

@Moonshane that's a lovely piece of kit, would love to have a look through that. Did the EQ5 handle it ok (guess it must have!)? It doesnt look like Orion Optics make this scope anymore@jetstream

Yes the eq5 was fine for visual but probably only only on calm nights ; 0)

[Moonshane]

Btw I think oouk still make these but only to special order

[Chris]

3 hours ago, nightfisher said:

And of course another way to get a large Apo cheap is a Maksutov, with the benefit of being able to use bino viewer with no mods

Very true! I did once have a 127mm Mak, and with WO BV's it was tremendous on the Moon! Another Mak or C6 is on the cards for me at some point  

[nightfisher]

5 hours ago, Chris Lock said:

Very true! I did once have a 127mm Mak, and with WO BV's it was tremendous on the Moon! Another Mak or C6 is on the cards for me at some point  

After i posted about a Maksutov/Bino viewer it did start the cogs spinning, i bet a 150 pro with bino`s would be a hard act to beat

[Moonshane]

A 120ed with BVs is a hard act to follow. Trust me.

[nightfisher]

13 minutes ago, Moonshane said:

A 120ed with BVs is a hard act to follow. Trust me.

Dont panic, i cant afford a Binoviewer, even though the 120 has failed to really impress me i am duty bound to keep it for the harmony of the forum

[Moonshane]

Bob round to mine sometime and have have a have a lunar session

[jetstream]

15 hours ago, RobertI said:

Sorry @jetstream what is MTF?

Modulation transfer function. Assuming the light containing the image we view is perfect we can only degrade the image and not improve it with optics (or seeing, thermals etc) ie Suiters filtering concept. The graphs tell the tale... and there are many.

[Moonshane]

Wow. Something else to add to the list of things I know nothing about 

I suppose our eyes also degrade it depending on our prescription?

[jetstream]

6 hours ago, Moonshane said:

I suppose our eyes also degrade it depending on our prescription?

I hold the personal belief that the whole optical chain, including eyepieces and eyeballs can affect the MTF. Many educated people don't think eyepieces can however. Visual acuity with regard to viewing is another puzzling thing, for me anyway.

https://www.cloudynights.com/topic/566542-visual-acuity/#entry7704523

I also believe that an excellent goal is to get a truly diffraction limited optical system.

Edited April 24, 2017 by jetstream
more info

[John]

14 hours ago, jetstream said:

Modulation transfer function. Assuming the light containing the image we view is perfect we can only degrade the image and not improve it with optics (or seeing, thermals etc) ie Suiters filtering concept......

I don't claim to understand the detail of the graphs but I get the concept. I think it chimes with my preference when acquiring equipment which has always been driven by trying to get the best optical performance that I can afford and not to put anything in the optical chain that really does not need to be there or is of unknown optical quality. My observing eye has to be the exception to this though because it's the only one I have

 

Edited April 24, 2017 by John