Why You Should Start Shooting In Long Focal Length In 2025
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- Опубліковано 9 лют 2025
- Long focal length telescopes: For ages, astrophotographer advice was generally to avoid them due to the additional challenges they posed. But times have changed. Long focal length is much more manageable now, and for a little extra effort, they can open an extraordinary window on the cosmos.
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#astronomy #astrophotography #space #nebula #stars
It's interesting that I had just been contemplating doing some shooting at the longer FL and you came out with this video a day later. The field of conciseness is an interesting thing... ;-)
Just ordered myself a new setup consisting of C8 EdgeHD + 0.7 reducer, IMX571C camera, OAG, Wave150i mount and Minix Z100-0dB PC before the tariffs let the prices skyrocket... Clear skies everyone :)
Sounds like a wonderful rig. I hope you let me know how you're making out with the 150i. It's a mount I've had my eye on. In Canada, the tariffs are likely to drive Chinese prices down, so I think I'll order one in spring.
Nice rig, don’t forget to order the hand controller which they sell separately for the 150i. What will you use for a filter setup and guide camera. I could never find any guide stars with the Celestron OAG so I used a separate guide scope.
@@mr.b3054 I have no use for the hand controller. Setup and initial tests will be done via the mobile app and after that I'll be using NINA. For guiding I have either a ZWO offaxis guider or a 60/240mm guidescope. The OAG would definately be better suited for the longer focal length though. For 120seconds exposures the guidescope should still be fine at 1420mm however.
@@jrs77do you need the hand controller for firmware updates?
@@mr.b3054 No. This can be done via the USB-port. The handcontroller is 100% optional which has been assured in the two Sky-Watcher livestreams introducing and showcasing the mount.
I started out with the 8SE. Phenomenal telescopes for the money!
Given its versatility and optical quality, absolutely. It's why they have a C11 on the ISS. When I eventually build the second observatory, I will likely get a C11.
Perfectly timed video. I am setting up my 1900MM FL rig again after imaging solely with a TOA130 for the last year or so. I had forgotten how challenging it is. The main issue I have this time of year is warmer days and cooler nights, so I'm chasing focus all the time and with an OAG, that affects guiding as well.
At that focal length, the OAG is probably the best option. We get large temperature changes here, too, especially during spring and autumn nights. I set my sequence to assess focus every time the filter changes. I lose the time focusing but the images are always sharp that way.
Looking forward to learning long focal length this year. Up until now have I have used hyperstar without guiding. Really was very easy compared to some of the hyperstar horror stories I've heard.
Planning on using the 6.3 reducer this year, and learning guiding with my oag. Then on to trying my hand at planets at the end of year.
I have all the same equipment as you, right down to the mini pc.
Guiding with a OAG really is no more difficult than guiding with a guide scope. I have not personally encountered any of the horror stories I've read about difficulty finding guide stars. One thing that helps, though, is not to use a camera with a full size sensor. That leaves room for the OAG to a bit further into the light path and pick up more stars.
Lovely images, but a fair comparison of long v short focal length systems would keep aperture constant. I have been imaging w a 200mm F4 Newtonian (Vixen R200S) at 760mm, and have just acquired the VMC200 w .63 focal reducer working fl 1228 mm. Just starting to make some comparisons for galaxy imaging, but guiding 5 min subs has been fine in my Bortle 5 skies. Hadn’t thought about the advantages for nebulas.
I get where you're coming from, but it's physically not possible to keep aperture constant without a huge change to F-ratio. I used images from my WO 81mm refractor which shoots at 447 mm and my Celestrom 203mm SCT which shoots at 1280 mm because they have about the same F-ratio of f/5.9 and f/6.3 respectively. Were I to increase the refractor's focal length to 1350 with a Barlow lens, I would get an f-ratio of f/17.7. If I were to decrease the SCT's focal length to near the 450 focal length range with reducer, I would likewise drop the f-ratio to f/2.x. To keep f-ratio constant, aperture must increase.
I went straight from a 60mm refractor (1st OTA) to a 10" f/4 Newtonian last year and have been very happy with it. Still want EdgeHD 14", but this setup will keep me busy for a few years.
Which Newt did you get?
@@SKYST0RY The Apertura 10" f/4 Newtonian from High Point Scientific. I suspect it's originally a GSO OTA, given that iOptron (and Orion, before it closed) have (had) similar models. But the Apertura came with a few extra features, like a built in primary fan. Paired with the Baader Mark III Coma Corrector, it's been fantastic for astrophotography.
I literally just yesterday pulled the trigger on an Edge HD 8" (2032mm) to supplement my current RedCat 71 (350mm). If nothing else, this will just be more flexible. Shooting the moon/sun? Go native. Shooting a DSO? Put on a reducer and get a bit more speed and FoV. Taking a peek at Jupiter? Give a barlow lens a shot. Conquering the Pleiades? Slap on a HyperStar and bask in f/1.9 at 400mm.
"But tracking is more difficult and collimation is a thing you have to you do now."
If the hobby were easy then it wouldn't be fun!
You know, despite the extreme temperature ranges where I live, I have never had to recollimate my SCT. It's stable as a rock. Granted, it sits on a permanent pier in the observatory, but still, SCT collimation is very stable.
one can dream...very nice images! thank you for sharing info and time! any suggestions for a budget high focal length scope with very good optical quality? I am using a askar 71f for now as i learn
I honestly think the Celestron C8 is one of your best options. They've been around for ages and there are frequently good used ones to be had.
I am actually currently shooting IC 434 with an 8" EdgeHD with 0.7 reducer, effectively putting the focal length at about 1400mm. I am using the ASI294MC Pro. This video is great, and relates actually, most people shoot this target around 400mm. I have actually shot the Trapezium cluster in IR at the 1400mm FL, it's really interesting.
Please share the link to see the outcome photo. Also, what IR camera were you using? I've been wanting to get an IR sensitive camera for quite some time.
Thanks for another great video. I've recently started shooting at longer focal length with my Tak FC100Dl at 900mm on an AM5. Really enjoying the higher detail I get at this field of view and haven't found it nearly as difficult as a lot of the internet/forum chatter would have lead me to believe.. Have just acquired a second mount (Wave 150i), so want to get mu C8 up and running as well. Are you using the Celestron reducer or one of the 3rd party reducers like say the one from Starizona?
I'm just using the Celestron reducer and getting phenomenal results on it. All the images on my Astrobin made after January 2024 were made with the Celestron C8 and Celestron reducer/corrector.
@@SKYST0RY Thanks, good to hear. I picked one up for visual a while back so I'll start with that and see how it goes. Have you ever shot at the C8's native focal length?
My eq6-r pro has trouble with my c11 at native focal length, and even with the 0.63 reducer. It's fine with hyperstar at 540mm F1.9, but I'm looking for a mount upgrade to shoot at 2800mm. Great video!
Have you tried tuning it? The EQ6 is famously reliable, but quality control has resulted in some that were a bit better than others. QC went up as time went by so newer ones, I have heard, tend to be better than older ones. Tuning often improves these issues. If your turbulence is poor, you will get bad guiding no matter what. On nights of high turbulence here, I have had guiding errors of as much as 4 RMS. Fortunately, that's rare and most good nights also have good turbulence.
@SKYST0RY I went through it completely. No backlash, nothing sticky, PEC trained, phd2 calibration and guiding assistant always look great. It guides reliably at 0.5-0.9" with my c8 on it, but it seems the porky c11 just pushes it a bit too much. 1.2" rms on a good night with the c11, which is sufficient for nebula season with the hyperstar. But galaxy season is coming up, and I'm considering getting a CQ350 or an eq8-r for it!
Glad that I found this video, as I was about to give up shooting long FL. The only issue I have is a noticeable vignetting when I use 0.63 FR. Can you please advise about proper flats for SCT? When I do AP with my 5.6 ‘frac (F/7 +0.8 FR), I have no prob getting decent pictures and flats compensate for whatever imperfections do exist. On the other hand, the same methodology proves to be insufficient to calibrate off the SCT vignetting. How do you shoot your flats to compensate for the vignetting? Cheers!
I haven't had this issue, but I do have several videos on shooting flats. If you go to the search menu on my channel and type "flats", it'll bring them up. I shoot flats with the NINA Flat Wizard. Sky flats if the mornings are clear, or light panel flats if not. It takes only a couple minutes with the Flat Wizard. But, either way, it's been problem-free for me. My first thought is you may have to adjust the peak of your flat light curve, and if you are using a full frame sensor, that may need to be calibrated.
@@SKYST0RY Thank you. Peak position was my first suspect, so I ran a gamut of tests moving the peak anywhere form 10k eDU up to 40k. The effect of those changes was marginal. I also ran tests when I was shooting flats either "white balanced" or with all channels set @128. I see that you use mono camera, so this is what you are not concerned about :) My current suspect is the reducer, as without it the vignetting is significantly less pronounced. Having watched your video, I thought that probably my exposure is higher than needed, as in m case it is about1.5s, while in your video you ar way below 1 sec. Also I use SharpCap for flats and the results with its wizard a disappointing a bit, but I attribute that to a "user error" ;) Cheers!
You said you have a 585 sensor camera? Do you bin it at that focal length or do you keep it at bin 1
TBH, I never bin when shooting images. I hate what the increased pixel size does to image resolution.
What do you use to plate solve with? I am trying to use ASI715MC with C5 and 0.63 reducer and I think I am just outside what the ASI air can do. I have no problem switching to NINA apart from the learning curve, but it has to happen sometime. How do you make the C8 work with the reducer are you using the 585 chip you mentioned in the video. Without the reducer how do you get it to work then? Plate solve on the guide scope?
Plate solving in NINA has not been an issue at all for me, at any focal length or with any telescope. The key thing is you need good focus before you even attempt it. That is absolutely critical. Get that focus as good as possible. And make sure that you have the date and focal length set correctly in the plate solver options. The focal length should be set for the apparent, not actual, focal length. In other words, if the math tells me my SCT as a FL of 1280 with the corrector/reducer, but an analysis of the image reports 1263 FL then that is what should be set into the plate solve parameters. There can be this small variation due to things like slight optical differences or slight changes in alignment or positioning of equipment. Once that is all in place, plate solving is quick and efficient.
@SKYST0RY Thank you for taking the time to get back to me and thank you for sharing your knowledge and passion for this amazing hobby. FYI I am imaging the Iris nebula this evening to see if GraxPert noise reduction is destructive of the nebula detail or not. The search for knowledge is never ending.
Interesting comparison between focal lengths, but I think that without the increased aperture of the SCT you wouldn’t be getting the same results. Is there a specific reason that you didn’t use the native f/10 focal length of the SCT?
I get where you're coming from, but it's physically not possible to keep aperture constant without a huge change to F-ratio. I used images from my WO 81mm refractor which shoots at 447 mm and my Celestrom 203mm SCT which shoots at 1280 mm because they have about the same F-ratio of f/5.9 and f/6.3 respectively. Were I to increase the refractor's focal length to 1350 with a Barlow lens, I would get an f-ratio of f/17.7. If I were to decrease the SCT's focal length to near the 450 focal length range with reducer, I would likewise drop the f-ratio to f/2.x. To keep f-ratio constant, aperture must increase. Right now, I have not had a practical cause to push to the f/10-fl2032 range due to the FoV occupation of the targets I have been shooting.
Hello again! Very informative video. I have this question for you if I may, I have a C8 non EdgeHD, what is your take on the EdgeHd vs plain SCT, do you think it's worth the price difference ? Have you compared the two side-by-side? I have seen one video that did this, and I really tend to think that the EdgeHD is a bit overblown for the real difference it offers in the field, the optical differences seem really small and seem to be easily handled by today's Blurx etc. I understand that you use an SCT (non EdgeHD)... what do you think (not to put down EdgeHD users)?
I have never owned the Edge but the reports I have read from persons on Cloudy Nights that have tried the Edge and non-Edge variants often indicate the Edge isn't worth the price. It's basically the standard model with a corrector built in. There have been further reports (I think by Lamb) that the Edge is inclined to suffer artifacts when the ring defogger is used. The standard model gets this, too, but to much less of a degree. Because of this, I have no plans to buy an Edge.
Do you drizzle you stack?
Yes, I always drizzle. I've tested it and posted the outcomes in other videos, and drizzled DSO images always come out superior.
Ai vids are an absolute NO for me as well as vids with just music. No thanks!
just fyi, nothing in this video is AI, that’s his voice and his pictures…
I agree. Those really suck!
Lol 😂 he thought his voice was ai priceless
Agreed!
This vid was great.