Introduction and a simple question

[Lister5]

Hi everyone,
I'm jumping into astronomy with my family. I've been a decades-long photographer and I've done a lot of work with macrophotography with my SLRs, as well as setting up scopes for hunting and target shooting (definitely realise the dichotomy there )

Anyway, I picked up a second-hand Orion Astroview 6" reflector in fantastic condition, and I set myself to immediately learning how to collimate the mirrors, configure and use the equatorial mount, and I grabbed some new midrange eyepieces and a good Barlow lens. I'm trying not to overdo it right at the moment, but I believe the lenses were with the telescope originally and thought some basic eyepieces would be good to start with.

On my list of to do is to carefully and properly clean the mirrors (they look pretty good but I figure it won't hurt), and I was thinking whilst I have everything apart I might look at flocking the tube.

Once I work out my lens set up a bit more, I'll probably start investigating some better and alternative glass as I'm a big believer in good quality glass for the best results (that's the photog in me being OCD ). It intrigues me with the use of different configurations of lenses, tubes and combinations just how complex and customisable telescopes can become. There looks to be plenty to learn there and keep me occupied anyway.

I'm only setting some really basic goals of the planets at the moment, but I did run into a question regarding the primary mirror. The documentation with the scope and everything I've read so far, there is (in theory) three locking/fixing screws and three adjustment screws on the primary mirror.

I removed the metal cover from the back of the primary and I found only three adjustment screws, however I did find holes for what I'm guessing are locking/fixing screws. I have moved the scope several dozen times already and nothing seems to have moved in terms of collimation, but I couldn't help but wondering if someone forgot to put something back sometime in the past.

I can certainly add some photos if it helps to see, but it's really just a metal cover over the mirror with the three screws to hold the cover, and removing the cover three adjustment screws. The holes for the metal plate and the empty holes are very close to each other, but I'm wondering if they are really necessary or indeed how they would fit with the metal cover in place. Unlike a lot of the photos I've seen, the mirror is not covered by anything at the back with the metal cover removed - it's just glass.

Anyway, look forward to reading more, playing around a whole lot more, and maybe one day getting around to joining my love of photography with some burgeoning astronomy love.

Cheers,
Sean.

[Saturnine (Jeff)]

Hi Sean
Welcome to the forums, you seem to have a background that should make astronomy a bit easier to navigate your way around and hope you get enjoyment from your scope purchase. Personally, I wouldn't be too fussed about cleaning the mirror or playing with the collimation until you've had a bit more experience with using the scope and learning a bit more about the ins and outs of newtonian scopes. Mirrors with a bit of dust or haze will work surprisingly well and before touching the collimation , get a sight tube and check what the mirror alignment is like, it may be in good collimation anyway.
The 3 holes you mention may have grub screws in them, that sit below the mirror cell exterior. Most newtonians are open at the back , having the rear of the mirror mostly bare apart from the cell support around the circumference, is to aid the mirror cooling to ambient temperature when being set up, though a 150 mm piece of glass doesn't have much thermal mass so should not take long to cool down, or warm up if taken out of an air conditioned environment to a warm night outside.
The scope itself is not an ideal planetary telescope, a bit short in focal length, but it will still show Saturns' Rings and Jupiters main cloud bands and moons.
As you may be well aware , there is plenty of info online about newtonian telescopes and how to look after them and lastly just enjoy using it .

[Lister5]

Thanks Jeff. I think I've got the collimation sorted enough for the moment using a Cheshire eyepiece. Everything lined up well with just some minor adjustments to the secondary and primary needed. I wasn't sure about a laser collimator as I've found bore sighting with laser tools to be sometimes frustrating.

I had figured it might be best to leave the cleaning for the moment. There really isn't a lot of dust visible and there's no marks or smudges I can see.

I haven't had a chance to play with the new eyepieces yet, but you raised an interesting point about the aperture size. Am I being a bit optimistic for planetary viewing at 150mm? I know it's only F5: so not enormously fast (I'm contrasting with my prime SLR lenses at as low as 1.4), but is it a question of the amount of light, magnification or both? I honestly landed on 150mm as it seemed like a reasonably portable size with a good mount. I'll be the first to admit I'm not all over the differences in terminology and effect. I do know I prefer larger objectives on my rifle scopes, binoculars and spotting scope, but they are all variable zoom, so a different game again

[Saturnine (Jeff)]

I haven't had a chance to play with the new eyepieces yet, but you raised an interesting point about the aperture size. Am I being a bit optimistic for
planetary viewing at 150mm? I know it's only F5: so not enormously fast .

Telescopes for planetary and lunar viewing and imaging work better at longer focal lengths, your scope will still give an ok image but as the planets are relatively bright objects, astronomically speaking, you don't need a fast system. Most scopes used for the planets start at F8 and up, the images that you see on here and other websites of close ups are more often taken at F15 /20 or even longer, as cameras for planetary captures are quite low light sensitive.
The 150m aperture is sufficient , though bigger is better but at F5 you will need to barlow at X3 to X5 to reach a suitable focal length. This then puts more emphasis on how well your scope is collimated and tracking. Have included an image that I took a few years ago with an 150mm F8 newt and 2.5 Powermate, so increasing the F ratio to 20, was very good seeing that night, which is a governing factor when imaging the planets as all too often the "seeing" is crap ( technical term).
Good to hear that your scopes collimation seems good atm and will leave it alone for now , use and enjoy.

[Lister5]

Originally Posted by Saturnine

The 150m aperture is sufficient , though bigger is better but at F5 you will need to barlow at X3 to X5 to reach a suitable focal length. This then puts more emphasis on how well your scope is collimated and tracking. Have included an image that I took a few years ago with an 150mm F8 newt and 2.5 Powermate, so increasing the F ratio to 20, was very good seeing that night, which is a governing factor when imaging the planets as all too often the "seeing" is crap ( technical term).
Good to hear that your scopes collimation seems good atm and will leave it alone for now , use and enjoy.

That is an awesome shot there Jeff, something to aspire to. I'm hoping to get a chance over the next week to do a bit more playing around with the new eye pieces, and break out the Barlow. If I'm reading the data right from Mateoblue it should be reasonably good weather in the next few days, with Jupiter and Saturn in relatively good positions.