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Everything posted by Jessun
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Dual RASA 8 rig - nearly there
Jessun replied to gorann's topic in Discussions - Scopes / Whole setups
Hej gorann, I have shelved what little I have left of a triple rig and I am no longer an active imager - if that is even a word... My view from experience is that once aligned, the OTAs should be left alone. By that I mean that after painstakingly aligning two or more OTAs, a new attachment point will just create more issues. I doubt that a bar can be secured without upsetting the initial alignment, or introduce another thermal expansion issue. You will most certainly end up confused as to which bolts to adjust, much like trying to cut the four legs of a chair dead even, in order to prevent the chair from behaving like a metronome. I shimmed my first triple rig to decent alignment, and for my second triple setup, with heavier OTAs, I used two of the saddles that you use. I found that the OTAs behaved in a similar way and there was no individual flexing worth noting. They all seemed to warp in unison. I never ran multiple reflectors though, so I would tend to agree with the comments that focus on the mirrors, rather than the mounting hardware. Good luck with the mission! /Jessun -
Approaching 4 years from first asking a question, poor Jez is quite possibly none the wiser...
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Hi there is no glass in the focuser or in that end of the tube, only at the front. EDIT: No Jessun, that is most probably 100% wrong... I don't know that focuser but I hasten a guess that where it rotates is where you can take it apart. I would hesitate to unscrew the entire focuser where it mates the white tube. The focus knobs come off if you have the right allen key, but these are grub screws inside there and there's only so many times you can do that before the screws are destroyed. I would leave that as it is. /Jessun
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I suggest not spending money on LP filters. I have tried them all. Just balance the curves in your processing software and it's dealt with free of charge. /Jessun
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Are you already running a laptop remotely?
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Small PCs like that one are great sitting by the rig and run over Wifi with a remote control program. I used to run three Shuttles at the same time from a laptop. /Jessun
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"New to me" - Astro-Physics 1600GTO - Big thanks to Jesper!
Jessun replied to rrb24's topic in Discussions - Mounts
Pleasure, Roberto! I'll look out for you on Astrobin 🙂 /Jesper- 1 reply
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Focal length of the SW finderscope used as a guidescope?
Jessun replied to SmokeyJoe's topic in Getting Started With Imaging
Is this of interest though? I mean not the thread as such but the FL of a guide scope. PHD and other software don't mind really. /Jessun -
I agree with what is said above by other members. It's been some time since I used my Canon DSLR so my advice about stacking was not clear. I assumed a run with the filter and another without it. Sorry for the confusion. As to the rain effect, I'm sure you can search for 'rain' or something and find some threads on the topic. /Jessun
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I'd say that is a 'normal' result looking at the time and number of subs. DSLRs often produce these rain like streaks and I never found a good way around it in processing. I had some software that had an anti-streak routine but can't remember which one it was. For stacking, you are limited by your data. With that I mean that after stacking you will be able to pull out whatever it is you are looking for. But for this target, very Ha rich, I see no reason why you couldn't stack the whole lot AND separately stack the red channel to have a look at what's in there. You can use this as a separate layer, if layers are something you are familiar with. /Jessun
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I used to run Shuttle units with Celeron processors via Remote desktop. Worked a treat. I'd preprocess 'locally' and then just send one file indoors per session. /Jessun
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How much data are we looking at here? The processing looks sound to me. A tad high in contrast and some - like me - try hard to tune the green down and try to hide purple star halos, but there's no need to do that. This looks very HST authentic. /Jessun
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So why isn't aperture important for DSO's?
Jessun replied to biondi's topic in Getting Started With Imaging
vlaiv, I think it's easy to do away with numbers and pixels to grasp the basic concept of F ratio. The number is a fraction with no end to the decimal places, and it has no unit. Then we put something tricky to observe in front of the lens and something even trickier (a sensor) at the focal plane and practical matters kick in in abundance. I enjoy these discussions but I don't want to be the broken record on the subject... It's often the case that your OTA slips, the sensor ices over, the laptop crashes or clouds gathering above etc, way before you really have to lose sleep over the F ratio of the rig... /Jessun -
So why isn't aperture important for DSO's?
Jessun replied to biondi's topic in Getting Started With Imaging
My response above is to DrRobin -
So why isn't aperture important for DSO's?
Jessun replied to biondi's topic in Getting Started With Imaging
Very neat. The risk is of course to over complicate matters sometimes. lukebl is right as we are all painfully aware that discussions on this subject never reached consensus. It's odd in a way that this is. /Jessun -
So why isn't aperture important for DSO's?
Jessun replied to biondi's topic in Getting Started With Imaging
I agree vlaiv. It's just optics and the 'sensor' should be though of as a white postage stamp rather than something that is segmented. Well done on the train question. It's just one of those riddles that only has a ratio at heart. 4 people ever solved it during the day I flew with them. One guy put in the speed of sound in a series of equations and came up with a number of miles. The simple ratio never clicked. /Jessun -
So why isn't aperture important for DSO's?
Jessun replied to biondi's topic in Getting Started With Imaging
You are right vlaiv as far as I'm educated. All practical considerations when it comes to taking an actual image are as we all know making it an almost impossible task. It is just so fundamental to understand F ratio at its core. Noise, pixel size, well depth etc are merely the constraints we have to deal with and don't quite play a part in understanding F ratio. There is for instance no F ratio myth as often proposed. As a side note I have attached an pic that I have drawn for most of the pilots I ever flew with. Some 3000 to date. Riddle: A man is fishing on a bridge. He is positioned one third in on the bridge. When he detects a train approaching he knows he has to vacate the bridge. He can either go to the left and Juuuuust miss being hit by the train or he can go to the right and Juuuuuust miss being hit. The man will walk at a pace of 6km per hour as he departs. Question, what is the speed of the train and how far away is it when he starts walking? You can answer in a unit of your choice if you don't like the metric system. /Jessun -
So why isn't aperture important for DSO's?
Jessun replied to biondi's topic in Getting Started With Imaging
vlaiv, I really like your thinking and you have the skill to formulate a model that works very well for you. I gathered that the OP wanted to go down to the logical basics, and for a more logical approach I think it's important to just accept it for what it is. A simple ratio between two measurements. The only other ratio I deal with daily is Mach number. It also has no unit. Mach is not a unit, although Americans often say something like "2 Mach". Don't ask me why this is. It's Mach 2. Ratio 2. Mach 2 is the same for a Lockheed aircraft or a Northrop aircraft. It's an absolute. Just like all F x telescopes are all equal. F ratio is just the same. It does away with any maths anyone cares to throw at it. 80/10=8. No number is more important than the other. 80 is no more magic than 10 etc. The troubles only begin when we put a finite pixel at the business end and start drawing conclusions, or go down the route that astrophotography is somehow different from normal photography just because we have some very bright, small stars in the mix. /Jessun -
Awesome Dave! The Gimsom rams are all I have left from the Sky Crane as it was 'decommissioned' this year. Any pics? /Jesper
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Best high-ish end mount for permanent set up?
Jessun replied to MakeItSo's topic in Discussions - Mounts
I would like to see more user inputs on this one to add to the mix: http://www.jtwastronomy.com/products/mounts/ogem /Jessun