Orion Optics 300mm f6 Dob

[Laurie61]

This is my 300mm f6 Newtonian. It was made for me by Orion Optics in 2009. It has the ultragrade optics with a strehl of .992. The focuser is an electronic version of the standard 2in unit with single speed manual focus. The mirror cell has the OO fan fitted. I bought the OO dob base at the same time and also have rings and dovetail for mounting on a CGEM. I could not resist fettling it and it has some flocking and a baffle fitted, the mirror has also been moved back about 20mm along with the removal of the front reinforcing ring for one that fits around the outside. I found the dob base a bit low and have raised it about 4 inches. I fitted a temp sensor to the mirror for keeping track of cool down.

I have an interesting tale to tell about the mirror coatings, within a few weeks of collecting the scope a Robin managed to find its way into the out building where the scope is stored and left a “comment” on the mirror. I removed and cleaned the mirror as soon as I realised what had happened, happily, three years later there is no sign of any degeneration in the coating.

[John]

Very nice scope with some interesting modifications

I've not flocked 300 F/5.3 as yet. They do perform excellently though, don't they ?

Nice to know the OO coatings are robust. My mirrors date from 2007 but they were re-hiluxed in 2011 and look excellent. I don't find I use the cooling fan on mine - it seems to cool quite quickly for it's aperture as long as I plan ahead a little.

[nightfisher]

very nice dobsonian

[swamp thing]

Lovely looking scope. The simple lines of the OO scopes are a true example of form follows function, beautiful.

[scarp15]

Looks great, how well do you find the raised legs support the base, any vibration, damping down experienced?

[paul mc c]

Nice scope, they perform excellently, just curious,what is the covering on the scope and where is the baffle and does it improve it any.

Hope you luck with it.

[Laurie61]

Hi all, I don’t use the fan much either John, If its put out in good time to cool the scope is usually fine for visual. If I’m imaging planets I will run it for 15min before starting and sometimes leave it running while the camera’s going, the fan is smooth enough not to cause vibration. It helps keeping the scope outside in a garage. The scope performs very nicely, watching a shadow transit on Jupiter, on a good night, is a treat with the dark spot looking like a hole through the planet. Being able to see colour (Green) in the Orion Nebula was an unexpected pleasure. The raised legs are actually bicycle stabilisers, complete with wheels; they are made from U section steel and very rigid. The motion damping is barely any longer than for the standard dob base. I was going to remove the wheels but decided they would help on soft ground so left them on. The outer covering on the scope is foam matting; I have been experimenting with isolating the tube from body heat. I found with another scope that standing next to the tube would create a flickering effect in the eyepiece and thought it might be body heat causing tube currents. It has not been on long and I will probably need to wait for the colder weather to test properly. The baffle is about 18 in down from the front, fitted where the flocking stops and then there is more flocking at the primary mirror end. It was to try and compensate for not flocking the whole tube. It’s only 5mm deep so as not to vignette the primary, hard to say how much of an affect it has as a stand alone mod but can’t do any harm and looking down the tube it does seem to help make the tube darker. After reading about John’s positive experiences with an Equatorial tracking platform the next step will be getting one for this scope, although my stabilisers will probably have to come off.

[estwing]

those OO coatings are very good from what I hear...

[spaceboy]

Very nice!! and F/6 must give you some nice views with out the usual aberrations common in the faster Chinese scopes of the same aperture.

[Laurie61]

Very nice!! and F/6 must give you some nice views with out the usual aberrations common in the faster Chinese scopes of the same aperture.

I would have gone for a longer f ratio but I store the scope vertically on the Dob mount and the ceiling in the garage (telescope house) was a limiting factor This scope is 6ft 6in high as shown in the photo. The scope has a 57mm secondary giving a 19% obstruction.

[John]

I would have gone for a longer f ratio but I store the scope vertically on the Dob mount and the ceiling in the garage (telescope house) was a limiting factor This scope is 6ft 6in high as shown in the photo. The scope has a 57mm secondary giving a 19% obstruction.

Thats a great specification

I found my optical tube on the used market so it's not quite as bespoke as yours being the 300mm F/5.3 optical set with the 63mm / 21% secondary. Mine has curved secondary vanes though so, while there is diffraction no doubt, I don't see any spikes.

I've been very impressed with the performance of mine over the past few months it's been up and running, as I'm sure you are with yours

The EQ tracking platforms are excellent but do add a further 5 inches to the height of the scope. You probably would not need your base extensions if you use an EQ platform, in fact it would be better without to keep the centre of gravity down a bit.

[Damo636]

Very impressive scope