Review of the Stellarvue SVX090T Telescope for Astrophotography 

I think it is a wonderful instrument and I intend to travel with it this year. Thanks for the comment!

Once we get a decent stretch of weather I'll do some more detailed comparisons. Like always, as soon as I deployed this rig, the weather just had to disagree!

Awesome, thank you! I am running a session tonight - a multi target FOV including some star clusters and nebula. I have high expectations for this rig and I am sure it will produce wonderful results. Cheers!

Right on! Thanks for the comment. reflection Nebula are tough because there is actually a lot of dark nebula that also needs to be exposed - which can often lead to blowing out the core star that illuminates the scene. I have a thing for the Iris nebula - I like to use it as a baseline test for my setups. I will work on that particular capture and see how refined the image can become. Cheers!

Thanks, Larry. We will put this puppy to the test. Looking very good so far. All we need is a stretch of clear dark skies!

Thanks for the comment and question. If you inspect the Field Flattener as it is shipped from Stellarvue, you will notice that it is actually a lens element, a 7mm extension, a 40mm extension, and a 3mm camera adapter all screwed together. Stellarvue pre-assembles the flattener with those specific extensions so that the remaining backspace requirement is 55mm. This is to accommodate the typical backspacing of a DSLR sensor. But it is important to note, the actual backspacing requirement is the distance from the Field Flattener LENS to the camera sensor (which I calculate at 105mm). How you make up that distance is rig dependent. Stellarvue gives us a head start with 50mm in total extensions and adapter - leaving 55mm to go. My rotator, filter wheel, filters and camera came up short by 3.28mm. By adding those M69 extensions in the FF assembly, I gain the distance needed. Remember, in the end we want 105mm from the back of the FF lens assembly! Here is another scenario. Say I wanted to use an OAG that has a width of 20mm. Where do I find the 20mm?!?!. I could introduce that OAG and replace the 40mm FF extension with a 20mm extension. In the end, I will achieve the required backspacing. One final way of saying it is that the backspacing requirement FROM THE BACK OF THE ACTUAL LENS IN THE FF is 7mm+40mm+3mm+55mm = 105mm You can make that distance up anyway you like! I hope that makes sense!

@@AstroDNAObservatory Got it!! Thanks so much for the lengthy and detailed reply, David. I completely understand and I was only considering the 55mm from the back of the flattener, but not the 104.8 listed in the table on the Stellarvue site. This is great to know. Thank you again!

Hi Greg! I typically see Halos with very bright stars using either the Oiii filter or the Blue filter. I use the ZWO brand of filters, which I consider to be middle of the road. Some halo can be expected even with higher end filters. Now, I have not had enough experience with this scope yet to draw any conclusions. I will say that I am running a session tonight - first clear night in almost a month - and I will pay attention to the bright stars. I'll be sure and comment in my next video!

@@AstroDNAObservatory Thanks so much for your reply, David. I appreciate it. I'm using Antlia filters, which I've found to be very good as well as a bit less expensive that top tier filters. I've never seen any halos at all with those filters so my results with the 90T surprised me. Very happy you have some clear skies for a change, and I'll look forward to seeing and hearing about your results!

Thanks for the question Ken. So, when considering a telescope, you should consider both Aperture and Focal Ratio. The product of these two values will give you Focal Length. The longer the focal length, the smaller the FOV will be on a given sensor area. So, 90mm at F6 provides a wider FOV than say a 102 or 127 at the same F6. So this becomes a matter of what targets you would like to observe or image... 90mm at F6 gives you 540mm of focal length and some flexibility to image DSOs with larger apparent sizes (Think about larger nebulae and galaxies). The 127 at F6 is going to yield 762mm of focal length, and may not be better suited for targets with smaller apparent sizes. Truth be told, it is like a camera and collection of lenses. You often have several lenses in your bag for different targets and compositions. It is the same in astrophotography... Cheers and thank you for the comment/question!

@@AstroDNAObservatory Thanks for the good information.

It is expensive, indeed. We'll see how it performs over the next several months and see if there is a good case for the spend. I am hoping so, as this will be my travel scope. Cheers...