NGC2736 - Pencil Nebula

[jase (Jason)]

No problems Bert. At a glance, your Eta mosaic which I believe was two panels, I can match with 6 panels using the FSQ and 16803 chip of the Apogee U16M. Obviously, I'll have a little more resolution on my side operating at 530mm compared to 300mm (or 290mm as you suggest). Will see how things progress...no promises!

[RobF (Rob)]

Fascinating object Jase, thanks for showing.
Its looks like special effects from Star Trek to me - one of the more recent series that is - not TOS

[avandonk]

Jase I calibrated an image taken with the 300mm lens to a sky map with RegiStar. The number came out to be 292mm.

You utter utter B. making a better mosaic!

Bert

[DavidU (Dave)]

Bert, are you sure the element in the lens group is Magnesium Fluoride ?
Unusual choice for visual work I think.

Originally Posted by avandonk

Thanks Bert. I like your comparison. 300mm lens packs some punch thats for sure. I was admiring you Eta mosaic the other day. May use it for a scaffold image in due time.

I might start up a new business 'scaffolding for the gentry'. Just kidding.

Anytime anyone needs an almost perfectly rectilinear image as a scaffold for a mosaic with longer length optics just ask.

We are all doing battle with the limitations of our hardware. Collaboration is one way to win.

Actually Jase the 300mm Canon F2.8L is really a 290mm focal length lens. That way they can crib a bit to call it f/2.8 with a clear aperture of 104mm. To be f/2.8 at 300mm the clear aperture would be 107mm. The real limiting factor and expense is the single crystal of Magnesium Fluoride that is the heart of this lens. This single crystal element is in an 'o' ring sealed nitrogen atmosphere. There are also two ED elements in the main front lens combination. The front element is an optical flat which can be easily replaced if damaged.

I have had this lens out in the worst conditions for many years and it still performs like new. It is fully sealed against dust and moisture!

Sorry about the rant. Imagine how long the rant would be if I had a 16" RCOS!

Bert

[avandonk]

Originally Posted by DavidU

Bert, are you sure the element in the lens group is Magnesium Fluoride ?
Unusual choice for visual work I think.

Yes it is a single crystal of Magnesium Flouride 107 mm in diameter. It is easy to test this. Just shine a green laser pointer down the lens and the scatter from the laser beam disappears completely as it goes through the MgFl. There are no impurities or refractive anomalies to scatter the light. MgFl is isotropic if that fact helps.

FPL 51 and 53 glass is a mixture of MgFl and glass. I will leave it to you to work out what is better. Low spectral dispersion is the game.

Bert

[Tom Davis (Tom)]

Excellent! So pretty!!

Tom

[Ric]

Fantastic capture Jase. the filaments look great winding their way through space.

A fine job indeed.

[jase (Jason)]

Originally Posted by Tom Davis

Excellent! So pretty!!

Tom

Thanks Tom. Pleased you liked it.

Originally Posted by Ric

Fantastic capture Jase. the filaments look great winding their way through space.

A fine job indeed.

Cheers Ric. Seems to be a target well suited to long focal lengths. Thanks for your comments.

[Garyh]

Beautiful detail Jase!
Might give this ago tonight..
Lookin good outside!

[DavidU (Dave)]

I see, that would be one expensive element ! I just found it odd they would use MgFl ( transition .12um - 8um) in a visual.The lens must be superb.

Originally Posted by avandonk

Yes it is a single crystal of Magnesium Flouride 107 mm in diameter. It is easy to test this. Just shine a green laser pointer down the lens and the scatter from the laser beam disappears completely as it goes through the MgFl. There are no impurities or refractive anomalies to scatter the light. MgFl is isotropic if that fact helps.

FPL 51 and 53 glass is a mixture of MgFl and glass. I will leave it to you to work out what is better. Low spectral dispersion is the game.

Bert