The focuser looks very tall. If you get a low profile focuser (GSO make one to fit) you may not have to move the mirror. Note if you move the mirror forward the secondary should increase in size to accommodate but you still may get vignetting from the focuser draw tube. However, increasing the secondary is OK for photo but detrimental for visual since contrast is reduced.
You will still need an extension tube for visual with a low profile focuser but changing your focuser is your best option overall. If cost is an issue then your current configuration is OK for photo. A smaller secondary just means light fall-off at the edges. There could also be vignetting from the tall focuser.
Guys, this is an "el-cheapo" scope. Focusser is 1.25". Secondary is not fully "silvered" - there are a few mm on one side that the machine missed! Mirror cell is very simplistic. Spider is on the flimsy side. Mechanics are very basic. Mount is an EQ(insert very small number). When Jen gets really serious, she will need a whole new setup.
I did monitor the secondary mirror size issue - I could still easily see the entire primary reflected in the secondary after we moved the primary up the tube so I expect no light loss from that. I agree with the possibility of vignetting by draw tube, particularly when it is 1.25" id.
I was worried about the primary mirror doing a "Leaning Tower of Pisa" impression as we moved the tube, but it held up well (Cheshire collimation didn't move much - horizon to zenith). Putting in the spacers and springs and removing the three push screws will improve primary mirror stability.
Jen, you can listen again
I was impressed with how far Jen got in one afternoon when it looked impossible a few times (eg. 1.25" focusser - yikes!). She got tracking underway, camera under control, a good focal range, and snapped a number of images - all in some hours. And retains the ability to do visual.
With a bit more practice, careful attention to polar alignment and drawing the best she can out of the mechanics with tender care, she will produce respectable beginners photos, I expect.
I think you had the right idea with the saw on the first shot. Shortening the tube and filing it square would have been fairly easy no? You reckon those extended bolts and spacers are going to hold the primary stiff enough that far from the cell? Just wondering how it's going to hold collimation.
Already held collimation better than I expected. There isn't much weight in the mirror and cell - I set the M5 bolts quite firm. But it will be much better with the spacers and strong springs, I'm sure. And easier to adjust the primary.
I doubt Jen will be cutting the tube. I wasn't confident it would work so I wanted to be able to restore it to original - which, incidentally involved three rubber o-rings. Initially, I just held the mirror further up the tube while Jen played with the camera and eyepieces to check she could get focus on both.
I was impressed with how far Jen got in one afternoon when it looked impossible a few times (eg. 1.25" focusser - yikes!). She got tracking underway, camera under control, a good focal range, and snapped a number of images - all in some hours. And retains the ability to do visual.
With a bit more practice, careful attention to polar alignment and drawing the best she can out of the mechanics with tender care, she will produce respectable beginners photos, I expect.
Im listening Eric, im listening That is a nice little write up there Eric you have boosted me with confidence now
hehehe eric im a uni student.! and hence on the tight budget a uni student gets.!
I guess you have to figure if you want to do visual or photographic, the both don't mix well! as i have come to figure lately.
Good luck jen, the 6" is a very big aperture still and you can get some really nice images out of it! Just remember if that 20 years ago a 12" was unheard of! 10 inch was just huge a 8" was an expensive but attainable large aperture scope, 6" was attainable. as for imaging... i don't know but it seemed very very drawn out and tedious but as the purist will say was worth every neck strain!
100% with you there Justin, i love the fact that i can set my imaging rig up, hit GO then sit there with a dob and look around! or chat to mates or curl up in the car seat and go to sleep for a few hours.!
I did monitor the secondary mirror size issue - I could still easily see the entire primary reflected in the secondary after we moved the primary up the tube so I expect no light loss from that. I agree with the possibility of vignetting by draw tube, particularly when it is 1.25" id.
I was worried about the primary mirror doing a "Leaning Tower of Pisa" impression as we moved the tube, but it held up well (Cheshire collimation didn't move much - horizon to zenith). Putting in the spacers and springs and removing the three push screws will improve primary mirror stability.
Hi,
Mine is a 2" focuser on the 8" bintel. I have'nt measured infocus required as yet, but will look out for some broad springs to support the mirror cell better. I guess automotive stores are a good place for some strong springs.
also thought of using a few pieces of double sided tape retaining one side of the nonstick sheath, and sticking it around the metal ring of the primary cell so that acts as a padding to keep the mirror ring centred in the tube should it tend to move sideways. so it will still allow it to move along the tubes axis but not perpendicular.
but not sure if the secondary will need to be replaced. will post some pics and hopefully get it ready for the sv camp.
Well done Suzy. A brave experiment indeed and gives heart to us amateurs back here with similar aspirations.
I'm hoping to do the same one day with the 10" strut dob I've almost completed. Easy enough to cut the strut tubes or carry extras for my attempts. it all just slides together. She (I've just personalised my scope ! ) seems to maintain collimation well even after pulling the UTA off and trundling it around the garden. It just drops back down over the strut tubes and away she goes like a good thing.
I might be a bit late in the replying to this thread, but hey this pic shows some serious cutting action!!!
The tool used here is quiet accurate and clean in cutting a circle!
All it needed was some tender care with a angle grinder!
yes a little off topic..... not a 6" newt hehehehe
Bartman
BTW
nice pic of u (Jen)in post #4 pic 4....great angle and comp.
I might be a bit late in the replying to this thread, but hey this pic shows some serious cutting action!!!
The tool used here is quiet accurate and clean in cutting a circle!
All it needed was some tender care with a angle grinder!
yes a little off topic..... not a 6" newt hehehehe
Bartman
BTW
nice pic of u (Jen)in post #4 pic 4....great angle and comp.
..... but will look out for some broad springs to support the mirror cell better. I guess automotive stores are a good place for some strong springs.
Bunnings has a reasonable range of springs. I suggest you come to camp and we work out what is needed, then duck into Ballarat and buy there. They have a big Bunnings and we also found a good Bolt shop.
I'm hopeful what you can see in post #11 in this thread will work well on Jen's scope. I think that approach might also be fine on an 8"
Well, yes, I believe Richard is serious. As I understand it, he is replacing the spider on his scope and will need to mount the new one with new holes etc - so he probably has that in mind. But it is true, most adjustments I have seen made to scopes have been either lower profile focusser or at the primary mirror end.
Well, yes, I believe Richard is serious. As I understand it, he is replacing the spider on his scope and will need to mount the new one with new holes etc - so he probably has that in mind. But it is true, most adjustments I have seen made to scopes have been either lower profile focusser or at the primary mirror end.
Yeah but if you move the spider down the tube you have to move the focuser and redrill the tube too. Why move two components when you can just move the primary up and cut the tube?
Mirror cell is very simplistic. Spider is on the flimsy side. Mechanics are very basic. Mount is an EQ(insert very small number). When Jen gets really serious, she will need a whole new setup.
aww thanks Bartman 
No one likes my idea
