my new NGC7000 narrow band image
Posted 12 July 2013 - 01:33 AM
Terry - glad you found my reply Sky Watcher is introducing a FPL53 based objective f/5 for about $1k (this includes a flattener), and there is some about Vixen reviving the Pentax 100 or 125 design - so it seems that 'they' are paying attention! what in my mind I compare all to is the Orion FPL53 based 80mm triplet using an 'off the shelf' inexpensive focal reducer - total cost also about $1k and an stunning performer optically. but there too, the focuser is the weak part of the system when it comes to a fully loaded 8300M setup with a big filter wheel. In the case of the Orion it just ends up the length of the stuff on the focuser tube taxes it enough to be a problem at times.
But then too we at 1/3 the cost of the Tak FSQ, which I see as being 'in trouble' because of the lax engineering and poor performance of the focuser 'overall' because of the CAA issues.
Then for not much more $ Stellarview has this objective on a tube with a FT focuser. With reducer still less than half the Tak and a half stop FASTER and by my results flat enough for the 8300 chip.
Would be nice if someone went total overkill (I wish the SV had the larger FT focuser even if it looked funny) on the focuser for a change - it really makes all the difference, how can we make them hear us? It is not just great optics, it is that plus getting the CCD perfectly focused without worry. Not sure anyone has that in that bag - yet. But it's getting far more affordable and there is getting to be more competition.
Posted 12 July 2013 - 11:42 AM
Posted 12 July 2013 - 11:56 AM
Posted 12 July 2013 - 12:30 PM
Posted 18 July 2013 - 01:04 AM
I'm going to try and splice the two images together at some point after I learn how to do it.
Posted 18 July 2013 - 05:05 AM
Just over the last two days I've been looking into the 8300M and these 36mm Astrodon filters. I'll probably get these someday but the new 12" concrete pier and ROR observatory is at the top of my list at the moment. Do you think the 3nm filters are worth the added cost over the 5nm? I live in a blue zone (but very close to green) if that matters any at all. Thanks....Now I know who I'll be bugging when I'm ready to make the jump.
Posted 18 July 2013 - 03:32 PM
Monochrome for me is a necessity and I doubt I'd be imaging without it. I started with the Baader filters that are about 7 or 8nm for financial reasons. though they made a titanic difference from OSC here in the 'white zone', I often had gradient issues in my OIII and SII data. My Ha data was good as far as gradients though in comparing to other imagers using even more narrow filters maybe not as finely detailed or crisp'. My own opinion on the SII and OIII is go the narrowest you can afford. It's not just LP but Luna, and you can image anytime it is clear - no show stoppers. And what you get has that clean crisp look as far as signal to noise even if it's not very strong.
There is something to go into here that I think important. When you go monochrome and filters and use long exposures for nebula there are two ways to go about it from a time perspective. You can image sequentially until getting enough data for all bands, or you can go one band at a time. In the summertime when nights are short, it's taking me near a week of nights to capture all the data for the 3 filters using 20 minute sub exposures. It takes a lot of patience, no more getting an object overnight. (this just with ha/NII/OIII, I think RGBL it's possible)
Importantly you want to go long exposure for nebula in Ha/SII/OIII, the longer the better on most objects if not all. What really matters is that if you are going sequentially, that the filters are par focal. I had no problem with the Baader or now the Astrodons as long as they were a set. I did run into a big focus shift trying to keep the 7nm Baader Ha and use the Astrodon SII and OIII. So in the 'mixed filter' arrangement I would take the Ha and then go after the SII and OIII.
Another consideration with a mono/filter setup is the focuser quality is critical. It's more important than OSC. If you need to add a coma corrector or flattener or reducer on the focuser tube it adds length and any play at all, ANY, is magnified by the length added... tilt and offset, play, shift, all become a force to contend with.