Bahtinov Mask Focus Assessment in NINA and APT
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- Опубліковано 12 лис 2020
- It's back to the William Optics Redcat 51 and that means it's back to manual focus with a Bahtinov mask. In this video, I compare the NINA Bahtinov Analyzer, the APT v3.86-9 Bahtinov Aid, and the good ol' stand-alone classic Bahtinov Grabber software methods of assessing goodness of focus based on diffraction spike analysis. What are the pros and cons? Who wins? Watch and see....
- Наука та технологія
Great video! Used Nina Bahtinov analyzer with no problem. Would never have found the rectangle in the top left corner without this video! Gonna give Bahtinov grabber a try soon
Thanks for watching, Rick! Bahtinov Grabber is out of date, but still works and works best in my opinion
I just got a RASA and got "ok" focus one of out of three times with it. I just watched several of your videos on focusing and they were really helpful. I didn't know about using 1:1 setting and exactly how to use bahtinov grabber. I'm looking forward to getting back out there and working of getting perfect focus. Thanks for these videos.
Yeah, the 1:1 thing is pretty important. Good luck with getting focus, Taylor, and thanks for watching!
Exactly what I was looking for!
Cool! Thanks for watching!
James great study.. ive just been going by the HFR numbers for the stars and thats worked good so far on my 250 & 550mm scopes.. I got a new HD 11 now and when it comes to the moon.. I struggle to get focus because I don't have any numerical feedback.. Is there a way in NINA to get some kind of numerical feedback on focus for the moon?
Any help is appreciated.
Hey Tim. My approach is to slew to a star and focus with the Bahtinov mask or NINA autofocus, then go over to the planet or moon. As an alternative, you could use contrast detection in Sharpcap (a very good planetary/moon video recording software) or the contrast focus algorithm in NINA. I've never used NINA for this, but might be worth looking into. Thanks for watching, Tim!
Thought my mount was PA in NINA (< 1 degree fro both), but when I slew to coordinates, the camera is way off; I did get a warning it didn't slew far enough or something, to somehow change slew rate? but that warning went away when I next PA; what could be wrong? Used an L bracket for the camera, but that shouldn't be a problem
I use Sharpcap to do polar alignment and focus (with Bahtinov Grabber) and then switch over to NINA for imaging. The advantage of Sharpcap is that it is MUCH easier to tweak exposure/gain settings as well as switching cameras.
Good call, Michael. Sharpcap is very useful. You have a good workflow. I use the PoleMaster for polar alignment, but when I need video-like feed, I always switch to Sharpcap. I wish NINA had the capability to insert a pause after each image (APT can do this) so you could take a 5-sec shot, then pause for 10 sec to adjust focus, then repeat.
Very nice vid James.. like it so much..
I usually use Bahtinov grabber while looping in the bright star and adjust the focus.. rather than took a single sub and then use Bahtinov grabber to check..
Is that ok with this stand alone software ?
Thanks
Absolutely! That should work fine. Thanks for watching!
Hi James . Another excellent Vid of Information (VOI) . I assume the entered Focal Length , in Bahtinov Grabber , will be the calculated Focal length if you have a Reducer or if you have a Barlow ? Any insight on whether the final Release Candidate for APT might include an adjustable Focus Box ? I think it will be APT v3.90 when it reaches full release . /SRK
Hey Scott. You're correct. If possible use the calculated focal length from a plate solve. Well, I downloaded/installed APT v3.87 today. They didn't touch the Bahtinov Aid. I've brought up the size of the box in the forum before, but I didn't get much traction. Oh well. Long live the Bahtinov Grabber!
James
Great tutorial
Cheers
Thanks, Ben!
Informative video. Thanks.
Thanks for watching, Jim!
Hi James. I am having an issue with APT and needs more with a Windows 10 laptop and was wondering if you had this problem and solved it. When I start next emote with a virtual port, APT becomes unusable (laggy) when my mount and focuser (Celestron) are connected. If I start next emote with a virtual port, my mount and focused will not connect. I haven't even gotten to Stellarium yet. Any suggestions? Thanks (in advance) for any advice. Bob
I don't think I've had that particular problem. With the mount plugged in, go to "Device Manager" and pull down the COM port tree item to see what physical port your serial/USB device is assigned to. Mine says "Keyspan USB Serial Port (COM7)". That's the actual port you'll connect Nexremote to. My Device Manager also says "Eltima Virtual Serial Port (COM1)". Select COM1 as the virtual port in Nexremote. When you go into APT, shift-click on "Connect Scope" and select the Celestron Mount driver from the ASCOM menu. Then click on Properties and select COM1 for the COM port. Not sure if you'll have to do this in PHD2 if you've made the assignment here or not, but probably worth checking. See of that helps. Let me know. I hate problems like this. Astrophotography is frustrating enough as it is.
You have got to love autocorrect. APT and NexRemote. Thanks. Bob
Great information mate as just doing this now.
Rob b put on a reply concerning the Motorised Focuser would there be any chance that you Look into it , to show how you control it?
Thanks, Brian. Rob is very handy. Probably can make a focuser with duck tape and string. He brings up a good point in that the Ultimate Power Box I use has a focus controller capability built in so all I need are the mechanical bits. Never say "never" but I don't plan on going that direction in the near future. I've got 4 scopes and the Redcat is probably used the least amount of time during the year: SCT = 6 months, ED102 = 2-3 months, GT81 = 2-3 months, and Redcat = 1 month. So at about 8 imaging nights/year I don't feel the urgency to move that direction. Of course, once upon a time I wondered why people had more than one scope and then wondered why people used electronic focusers. Now I've got 4 scopes and 3 electronic focusers. Thanks for watching!
The biggest hurdle is making the cable from UPB pro to the motor since it involves crimping an RJ45 connector but you could easily cut up a ethernet cable. Now a little investigation is required and the best source is the robofocus/moonlight connection diagram which can be found on the UPBpro2 web page. Long story short forget the 12V connections and simply connect the 2 phases of the stepper motor to the UPBv2pro phase A and B +ve and _ve connectons. Triple check the connections and for shorts followed by standard UPBv2 pro software configuration but keep motor speed initially low. If the motor turns you are off to the races. You can reverse the motion in software or reverse both phases +ve for _ve and visa versa. If the motor runs erratically or simply vibrates reduce motor speed but if this still fails reverse either one of the phases. Due to voltage and motor inertia influences there will be a max speed the motor will turn. Increase the motor speed incrementally until the motor shows signs of mis-stepping and back off the speed to about 80% of max to ensure reliable running under all conditions. Do all testing when the scope is attached at mid focus and be prepared to quickly disconnect so as to prevent crashing the focus mechanism. Once you have the system under control run the focuser in to about 10% longer than minimum and set this point as 0. Now run the focuser to 10% short of full extension. Physically pre-measuring will help in this regard. Note the step count and set this as the max in software. Once you have all the data from the UBP software park the focuser at 0 and now configure your imaging software with the values from UPB pro software. I like to get an initial focus in daylight on a distant object and set this value as a starting point for any autofocus routine since all routines will fail if the initial starting point is far off. If for ANY reason you suspect the focuser has moved or slipped when disconnected redo the travel calibration.
THANK YOU James this really helped me! I don't understand why APT does not let you make a larger window?? Now I will try Bahtinov Grabber app with APT! Your Bahtinov spike was way better than what I am getting with my Orion 80ED 600mm f7 L-Pro filter and ASI0294 CCD camera. I last night started to use my first alignment star to focus on as it's much brighter than say M31 stars nearby. Would you agree that you should focus the closest alignment star to your target or really that does not matter?? I'm a new sub my friend!!
Hey Christopher. Thanks for signing your life over to the channel! Won't hurt a bit. Maybe a little. Yes, definitely find a nearby bright star for the Bahtinov mask. Alpheratz, for example, is very close to M31. This will be particularly true if you image with narrowband filters. Although, your L-Pro filter is "narrowband" so you probably need a bright star for that filter too. Play with the histogram settings and exposure to get good, long, well-defined spikes. May the focus be with you!
How did you mirror NINA image on your iPad? That intrigues me greatly.
Hi Ross. I use a free app called Splashtop. It's great for being able to adjust focus at the scope without disrupting the laptop. I also use it in the house when I'm not next to the laptop to "see what the imaging session" is up to. Give it a try. This app requires connection thru the web. Would prefer a direct wifi link. Oh well. Thanks for watching!
Are you converging on NINA as your main platform James? What version of NINA are you testing? Thnx
I think so. I'm using 1.10 HF1. Works great with autofocus on my GT81 (and I'll soon try out the ED102+NINA combo). It's a wash with my manual focus Redcat. Once APT gets their in-plan autofocus scheme up and running, I will certainly give it a shot though. I like the Flats Aid in APT better.
Perfect video ty
Thanks for watching!
I would like your opinion on how accurate Bahtinov masks are vs NINA autofocus? I installed a ZWO EAF on my Redcat 51. After an auto focus run in NINA producing an awesome curve, then checking with the Bahtinov the center spike is not centered. Some people on the NINA Discord say auto focus is more accurate then a Bahtinov mask. I'm not buying it. Great video, I love your channel.
Good question, Bill. I generally think (no proof!) that they are about the same (I regard "focus" as a wonderous place like a distant galaxy that we can imagine, but can never go there). With a Bahtinov mask, we focus on one star and use the "pixel error" as quantitative feedback on goodness of focus, then we take the mask off. But if you leave the mask on, you will record/see fluctuations in the pixel error from seeing. So there is variability there that we don't think about. With NINA, focus considers many stars across the field of view and averages the focus for all stars and may be more accurate on a field of view basis. The hyperbolic curve fit helps to manage seeing error. With the Redcat, if you focus with the ZWO EAF and then slide on the Bahtinov mask, you actually disturb the focus slightly that you got with the EAF. Focusing with the helical focuser on the Redcat is sooo sensitive. I think they need a fine focus adjustment. Anyway, long answer. I don't want to live in an astrophotography world where I have to slew off the target, go out and put the Bahtinov mask on, focus, slew back to the target, and resume imaging!
@@Aero19612 Great answer! Thank you for taking the time.
James, 5 months on, would you say you’ve migrated more toward Nina’s autofocus routine now? or do you still like Bahtinov Grabber?
I'm very much committed to the NINA autofocus routine and believe it gives excellent focus results. I still use the Bahtinov mask with the Redcat because it does not have an automatic focuser attached to it. Thanks for watching!
@@Aero19612 i tried apt autofocus here.
ua-cam.com/video/ngiozh2ZN5M/v-deo.html
it has promise!!!
Thanks for the video! Very interesting. I'm going to download/install the new APT. Several questions I'm interested in:
1. Does the autofocus only work for stars in that "little" window?
2. Why does the curve spike in the middle? I expected it to look like a hyperbola
3. Looks like you can take larger focuser steps
4. I stop guiding when doing a NINA autofocus because the focuser moves the scope and PHD tries to correct it.
@@Aero19612 Thanks for suggesting larger steps. I sure welcome the input.
spike: great question. you might have heard me in the video, asking out loud, “What in the world?” hahaha
stop guiding: smart
box: it seems so. only the stars in the box. i like that part.
i need more time, but , on the surface, it seemed super-effective for a first release of the autofocus routine.
If I had $1 for every time I've said/thought "What in the world?", I'd be retired today. I downloaded 3.88 and glanced through the User Guide. I gather this current incarnation is a replacement for the previous "autofocus" routine. It won't be until 3.90 that you can integrate it into imaging session scripts for night-long sessions (don't quote me on that).
I'd say that spike is a numerical problem with the algorithm. Maybe submit a screen shot of your curve (and any data that was saved) to the APT forum.
I like the idea of limiting the starfield to a region of interest (particularly in the center of the field of view) but I don't want that small of a box for my long focal length scope. It's early. They're still working on it. I'd say kudos to them for making nice progress!
By the way, I think your WyzeCam 3 does a better job than my v2. I really like having a live view of the telescope.
I don't use APT, but could you not just zoom out the image to effectively get a larger bahtinov FOV?
Hey Keith. Yes, but the issue is that the focus metrics assume that the pixels of the screen correspond 1:1 with the pixels of the imaging camera. So if you zoom out, you're creating an optimistic view of the focus and APT will tell you that you're in critical focus when you're actually not. That's why you have to be in 1:1 mode when using these tools.
Have you ever asked Ivo at Apt about making a bigger window he is open to feed back on his forum
It has been brought up. Ivo has said that it's processing intensive. I don't know. The original Bahtinov Grabber program does a pretty good job and certainly isn't slow. Oh well.
James don't forget the UPB pro can direct drive a stepper motor under imaging software control or even their own basic dumb focuser. What this means is with a simple toothed belt wrapped around the Redcat focuser and a pulley mounted to a gear reduced stepper you have a functional remote focuser. The motors I use with Crayford style focusers is a 1:27 ratio 0.4Amp bipolar geared stepper connected via the coarse focus shaft. The low current 0.4A is important not the 1.68A version. This combination will provide multiple steps inside the CFZ all the way out to about f10 with plenty of torque and will hold a setting even with the motor de-energised . I have seen some off the shelf solutions similar to this idea but the prices are ridiculous. Thingiverse has some 3D printed pulleys to go around the Redcat rubber if needed. The motors I have have came from ebay seller stepperonline. www.ebay.com.au/itm/27-1-Planetary-Gearbox-Nema-17-Stepper-Motor-0-4A-for-DIY-CNC-Robot-3D-Printer/171836706736?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 Have a Google around plenty of others have done the same.
Yep. The UPBv2 is a swiss army knife piece of electronics. Almost worth the price tag. Kidding. I actually think it is worth the price tag-can't say that about everything I've bought in this hobby. Not sure I'll go the belt focuser path. The poor Redcat won't be used all that much compared to the other three scopes. However, I must say, I did get spoiled with electronic focusers awful fast.
I love my redcat 51, but it is truly a pain to manually focus.
Agreed. If you’re interested, check out this video: ua-cam.com/video/EkChJxEiYiA/v-deo.html where I show results from the Pro Astro Gear 3D printed plastic auto focuser mount. It works really well. No more focusing by hand! Thanks for watching, Matthew.
@@Aero19612 Thank you. I've seen it, and similar solutions. I'll do something like this at some point, but right now I have other astro priorities.
Absolutely. Gotta set priorities. I was just “surprised” that this 3D printed mount could provide such reliable focus results. I liked the Redcat before, but the manual focus thing took away from that. This mount makes that scope so much more stress free to use. Put this, or something like it, on your “wish list”. Clear Skies!
Time and weather permitting - may try comparison between the ASIair Pro auto focus routine and the B-mask routines (Nina, APT and grabber) - have s different B-mask coming from NZ that produces more spikes and may be beneficial in collimation...
skylabs.co.nz/tri-bahtinov_mask.html
FOCUSING AND COLLIMATION TOOL
The Skylabs Improved Sensitivity Tri-Bahtinov masks are designed to obtain a very accurate focus and very precise collimation of reflector telescopes, including Schmidt-Cassegrain, Maksutov-Cassegrain, Classical Cassegrain, Ritchey-Chretien, Maksutov-Newtonian, and Newtonian Telescopes.
The Tri-Bahtinov mask improved by C.Y. Tan and Satoru Takagi has incorporated several enhancements compared to the traditional Bahtinov mask. It allows evaluating an even more accurate focus, and it also allows detecting and correcting a misscollimation of a reflector telescope.
This affordable tool is the result of vibrant cooperation and open-source contributions inside the astrophotography community.
Very cool, Jim! Let me know how it works. The interesting thing will be how the numerical Bahtinov spike identification/analysis algorithms in Bahtinov Grabber (APT) and NINA react to seeing 18 spikes instead of 3. Please comment back with your findings. Clear skies!
Mask is on the way...
Will report back results...
@@jimtaylor5802 Cool!