msacco

1 hour ago, Jiggy 67 said:

Telegizmos all day long. Re the Sun, they are lined inside with reflective material for that very reason (I am not aware of any other covers that have this). I leave my mount (and often the scope as well) for months on end in all weather with no issues. I wouldn’t use anything other than the TG

1 hour ago, bottletopburly said:

Can’t speak for other makes but my telegizmo has served my well inner lining starting to wear due to weight of cover , but I’d buy again and I’ve had it a few years maybe 4 or 5 .

That sounds pretty decisive, thank you for the help! TeleGizmos 365 cover that is.
Would you happen to have any recommendations regarding humid control? What is the best passive/active way of preventing dew under the cover? I planned on getting a big Dobsonian cover for my scope cover it until the bottom of the tripod.

I also wonder whether I should maybe split it into a tripod cover + scope + mount cover. What would be your recommendation?
E.g - both of these:
https://www.firstlightoptics.com/telegizmos-telescope-covers/telegizmos-365-tripod-cover-dual-material-w-solar-liner.html
https://www.firstlightoptics.com/telegizmos-telescope-covers/telegizmos-365-scope-cover-for-12-14-dobsonians.html

Or just one big dobsonian cover.

Thanks!

Hello, I'm looking for a cover to leave outside my mount, tripier, and maybe my scope as well if it would work well.

It would be a near permanent setup(will be taken apart once a month in a new moon I guess), I'll face high temperature and some humidity, rain is something to take into account, but there's not much rain here so it shouldn't be a big deal, same with strong winds, there are no strong winds here.

There is the TeleGizmos 365 cover which seems like the highest quality, but it seems like a very heavy scope against rain, and might not be as suitable against the hot sun, I'm wondering if there might be other things I should consider before I'm getting a TeleGizmos 365 cover? Budget is not a concern here, I'm looking at a big dobsonian cover at the moment to cover it almost completely with some room to breath.

Would love to hear some suggestions whether I should look at other solutions other than TeleGizmos 365, or just get one.

Thanks :)

8 hours ago, vlaiv said:

Ok, I understand now what you are after - you just want to make sure you preserved color that came out of camera as is, right?

Well, that is something that is not possible. We stretch our data and in doing so we are changing it. RGB ratios change when you stretch your data - and even if you stretch it in particular way that keeps relative ratios - you are again going to change what we see as color. Different stretches of same RGB ratio will produce different color sensation in our eye.

Bright orange is well - orange, but dark orange is no longer orange - it is brown to our eye - although it is same spectrum of the light - we see it as different hue.

Having said that - if you don't intentionally mess with color - you should be able to preserve raw color from camera "in general" (that is not accurate in terms of color reproduction - but can still be considered authentic as made by your equipment). Level of processing involved will determine how "accurate" or rather "preserved" color is (and there are different metrics of "preservation" - one related to light spectrum for example and one related to our perception).

If you again look at that image I posted - yes, OIII + Ha combination can produce orange color:

It can range from green/blue combination across pale yellow to orange and red.

In fact, when doing bicolor image - we often intentionally change color. That is because OIII signal can often be much fainter than Ha signal and image will end up being mostly red. If we want to show OIII structure - we will often boost it compared to Ha and that will shift color on above line towards green end.

So here is what "as is" raw color from camera looks like:

This is to be expected - Ha signal is much stronger and image is almost completely red.

If you want to show OIII a bit more clearly - well, you need to boost it separately. This is already deep in fake color territory - as we adjust color components separately.

Now that we made OIII stronger - it shows some structure - in upper right corner there is wall that still has dominant Ha but rest of the nebula shows OIII presence as well.

This shows that both of your versions are "correct" - just depend on how you define correct. If you want data as out of camera - linked stretch will provide that. If you want to emphasize otherwise weaker OIII signal - use unlinked stretch.

 

Thanks for the great comment once again! So is there some 'accepted standard' here on which of them should be used? Or it's really just a matter of personal preferences and each of them could be considered as 'okayish'?

3 hours ago, R26 oldtimer said:

As this is actually a narrowband image, there isn't really a "correct " colour. All nb images are really false colour representations. If I may suggest that you split the channels,  do a linear fit and then recombine.

Yep, I know that there is no really 'correct' color, and I'm not even referring to 'correct color' in term of what that area would look to the naked eye or something, but just specifically to my results, is there anything wrong? is it supposed to be that way and fine? By correct color I mean that this is the data I captured, and that I'm not inventing colors out of nowhere.

I'll try that, thanks

2 hours ago, vlaiv said:

I'm interested, but I don't own a copy of PI so would prefer in standard file format like 32bit floating point FITS rather than xisf that is PixInsight only file format.

On color topic - well answer is rather complex.

Fact that this is in essence narrowband image does not mean that it is necessarily false color. If color is to be consider accurate - we must decide what color are we talking about.

- Actual color of the object and stars - well, no luck there, filter used completely obliterated color information there

- Color of the light that passed thru the filter - we can talk about that color. Since these are emission type objects with Ha and OIII emission lines - we can talk about those colors.

You can choose to do actual narrowband color image - and you may be partially or fully successful in recreating actual color of the captured light. That largely depends on ratio of Ha to OIII signal.

Both Ha and OIII colors are outside of sRGB color gamut and we will here talk only about sRGB color gamut as I presume that intent is to display image online and sRGB is implied standard (we could also talk about other wider gamut color spaces - but only few people would be able to use that as it requires both wide gamut display and properly setup operating system that can display wide gamut images).

This is chromaticity diagram that shows all "colors" (at max brightness) that exists - with actual colors from sRGB color space shown. This is because other colors (gray area) simply can't be properly displayed by your screen / sRGB color space.

I outlined a line on this diagram. It connects ~500nm point at spectral locus to 656nm point at spectral locus. These are OIII and Ha colors. Any light consisting out of these two wavelengths (any combination of strength of each) will have color that lies on that particular line.

sRGB color space will only be able to show those colors that are in colored triangle along black line. All other colors that are left or right on that line will be too saturated green/teal or too saturated deep red. Computer screen simply can't display those.

If your image consists of combinations that lie inside triangle - great, you'll be able to fully display color of the light that passed thru the filter. If not - we must use a trick. There are several ways to do it: we can just clip the color along the line - if color lies in deep reds - we just show it as reddest color along the line that we can display. Similarly for OIII side. Another approach would be to do perceptual mapping - we instead choose color that looks most like color that we can't display - like dark deep red for Ha. This process is know as gamut mapping.

You can also decide to do fake color narrowband image - similar to SHO or HSO images - but you only have two wavelengths captured so you can only create bicolor image. Above is also bicolor image - but with accurate colors for the captured light.

With fake color - you can choose any bi color scheme you like - like HOO or similar.

In any case - before you choose any of these - you actually need to extract color data from you image. You used color sensor with duo band filter and you'll need some math to extract the actual data.

Look here:

We can see that L-eXtreme only passes ~500nm and ~656nm, but if we look at QE graph for ASI071:

We can see that 500nm ends up being picked by all three channels and so does 656. In fact we can write couple of equations:

red = OIII * 4.5% + Ha * 78%

green = OIII * 68% + Ha * 9%

blue = OIII * 45% + Ha * 3%

From these you can get OIII and Ha in several different ways using pixel math - I recommend following:

Ha = (red - green / 15.111) * 1.292

OIII = (green - red / 8.667)  * 1.46

If you want to get accurate color, then you need to convert Ha + OIII into XYZ value and then convert XYZ to sRGB, otherwise - just use Ha and OIII to compose RGB like HOO or other bicolor combination.

 

Thanks a lot for the detailed comment. Obviously, as you suggested, I'm mostly referring to the color of the light that passes through the filter.

My question is, would the correct thing be to combine my results to some sort of HOO? And would having these orange colors I got be considered 'incorrect'?
Again, it's not like I expect the image to represents the 'true color' of the area, but the only thing I want is to have the correct colors in terms of 'these colors are not added' or w/e, I want my image to be 'genuine' to the way I captured the data, which is OSC with a dual band filter.

Would the orange thing I got meet these requirements?

And as requested, here is the FITS stack
https://drive.google.com/file/d/12gzZhHJgppVhU7s--NQJwDYyo39EPZT1/view?usp=sharing

Thanks!

Hello, recently I imaged the pelican nebula with my ASI071MC Pro, Esprit 120 and L-eXtreme filter.

My processing workflow is usually as follows:
In pixinsight, doing background extraction and background work in general, sometimes I do some additional stuff but here I just stretched and wanted to go to photoshop with it.

My issue is - in pixinsight there is an option for linked stretch and unlinked stretch, I tried to process roughly the same both linked and unlinked stretches, but I don't know which colors are the correct colors and which aren't.

For reference, here is the unlinked stretch after background extraction:


Here is the linked stretch:


Usually, when imaging RGB unlinked stretch was always the 'correct' colors so this is what I've always done, but here I'm a bit confused by my ending results.
Here is the final unlinked stretch image(sort of, mostly did it to compare both images and see the potential of the image):

Here is the final(same as above) linked stretch image:

The colors of the unlinked stretch, which in most cases is correct for me, seems pretty off here...not sure how I got all this orange and it doesn't make sense to me considering the fact that the L-eXtreme should be mostly HA and OIII(if I'm not wrong?)
The stack itself seems pretty correct in my opinion as a bi-color stack representing the L-eXtreme, but the orange is still weird to me.
 

This is the unlinked stretch stack with ABE + some saturation:

As you can see, it goes orange quite fast, but is it correct?

Would love to learn some more about it. I know that 'correct colors' in space is a bit vague topic, but still, I think I should have some 'right' processing colors here, and I don't want to make up colors or whatever.

Here is the stack if anyone is interested:
https://drive.google.com/file/d/1snIAfOl53kuFEX24s2Zo48UtRFZR7l02/view

Thanks for the help

4 hours ago, wouterdhoye said:

Hi,

I have several planetary cameras. ASI 174M, ASI  224C and QHY 462C. All are great. My most recent purchase is the QHY and I'm very happy with it. It's really sensitive both in visible spectrum as well as IR. Noise levels are also very low. The most recent images taken on my astrobin page are with the 462. It seems that due to the sensitivity and the low read noise i can get away with stacking considerably less images to get a virtually noise free stacked image.

Now in the end you can take absolutley fabulous iamges with any of the planetary cameras sold today. even the "old" ASI120 is still one fabulous camera.

Thanks for the comment, I already decided to go with the 120mm only for guiding and staying with my 224MC for planetary

Hi, I currently own an ASI224MC for both guiding and planetary imaging, I'm building a second imaging rig and I need a new guiding camera, it looks like there are a bunch of new planetary cameras now by ZWO, so I'm wondering whether I'd want to move the 224MC to the new rig, and get myself a new planetary/guiding camera.

On the other hand, I could just get the cheapest ASI120 camera and that's it maybe...Overall I've been happy with the 224MC, but I didn't try other cameras, the 462 is only $50 more, the 385 is $100 more, the 178 should be pretty good as well I believe.

Would love to hear some suggestions

Thanks.

I'm doing planetary imaging with a C8 Edge HD btw.

2 minutes ago, callisto said:

I personally use these Filters-  https://www.altairastro.com/altair-2-premium-7nm-ha-narrowband-filter-309-p.asp

But I just realised your not in the UK so don't know about postage?

 

Mark

Yep I'm not from the UK, but I guess I can find some solution, how are these filters in general? Any halos? Do you have some Ha channel examples(maybe in a bright star region to see how it is)

Thanks

Hey, I'm looking for a Ha 2" filter and I'm really lost with all the different options. I'll start with some general information, I'm using the ASI071MC Pro, I own the following scopes:
Esprit 120, SharpStar 61 EDPH II, C8 Edge HD(will probably not be used as much).

I'll image from both bortle 6 and bortle 3 locations, so I guess that might be taken into consideration in terms of light pollution.
I don't have a set budget, but I don't intent to go towards the chroma/astrodon budget, that just feels way to expensive for me compared to other options.
I mostly thought of either the Baader 3.5nm Ha 2" filter:
https://www.highpointscientific.com/baader-enforced-narrowband-halpha-3-5nm-ccd-filter-fhalne-2

Or the Antlia 3.5nm Ha 2":
https://agenaastro.com/antlia-3-5nm-narrowband-h-alpha-ha-filter-2-mounted.html

But I've just seen that there is a 3nm Antlia filters:
https://agenaastro.com/antlia-3-0nm-narrowband-h-alpha-ha-pro-imaging-filter-2-mounted.html

They're a bit more expensive though. I tried to search for some comparisons, but couldn't find many, I looked at results using these filters, but 2 images could show very different things due to so many variables, so it's hard to actually see the quality.

So I'd like to hear some suggestions of people who maybe compared or tried these filters, which one would be better, or what's more recommended.

I'd also like to ask about whether I should actually get a 3/3.5nm filters - I'm usually not taking that very long exposures, around 3-5 minutes, since I'm using OSC camera, I've never really had the need for that for any target I imaged. As far as I understand, with a thinner filter, I'll need to take longer exposure to 'compensate' for the thin wavelengths, but since I'll be imaging from bortle 6(not that it's that great) and under skies, that means I might be able to get away with a thicker filter(e.g 5nm for example) for a bit shorter exposures and still have good results due to the light pollution being 'okayish'. One more thing to note, I want the Ha filter to be used for galaxies as well, I fear that for galaxies 3nm/3.5nm Ha filter would be too thin to give good results.

This is just my thoughts, maybe I'm completely wrong, which is why I'm asking here.

Thanks for the help!

1 minute ago, Stu Wilson said:

I'd hope so but only when I get to my laptop I'm afraid. Out at moment.

Sure np, I'm not in a rush

57 minutes ago, Stu Wilson said:

There u go. Image taken with qhy8l on ota sw200p

Sorry, I meant an unedited stack or single frame, do you possibly have any?
Thanks.

20 hours ago, Stu Wilson said:

If u do a search for skywatcher coma corrector they'll come up everywhere ie flo or rothervalley optics etc. Retail is 160 gbp or mine 115 gbp plus shipping

That would depend on the shipping costs, but I could get the 0.9x for a total of 140 gbp including shipping, so I'm not really sure it would make much of a difference.
Do you have an image taken with that coma corrector to see the corners?

Thanks.

16 hours ago, Clarkey said:

There is a comparison here that might be worth a look.

https://www.astrofotoblog.eu/?p=856

Thanks, I did see that, but the only corrector relevant for me there is the baader, so that still doesn't really give me a good enough comparison compared to the 0.9x/aplanatic, tough the explore scientific one looks amazing, but the price is a bit high for that and I'm not sure I'd want to invest so much into that.

14 minutes ago, Stu Wilson said:

Got a skywatcher  1 that's around 5 months old for sale if interested.

I used it for my sw200p but I've since got a new ota.

 

Stu

Which model is that exactly? I don't think it's the aplanatic?
Do you have the link to the product? I'm not from the UK so I wonder if shipping prices would make it worthy for me, but what is the price excluding shipping?

1 hour ago, Pryce said:

Could what you read previously be about one of the older(or non MPCC versions) ?

I'm assuming there's older and other versions since this one is called Multi purpose MK III. That could make sense 😅

That's.....surely possible.

So I guess that I don't really need to go with the aplanatic, but which one is better? The 0.9x or the baader one? The slightly wider focal length and f ratio could be pretty cool...
One more thing, any relevant information regarding adapters that I need to know? My camera is M42, but I have no issues with M48 as well.

1 hour ago, Pryce said:

I have the Baader one my self and I've not had any issues in testing. I never read anything bad about it before I purchased it and it also has stellar reviews on FLO.

Though he Aplanatic one should be better, but that's also reflected in the price.   Since you don't already have a CC I'm assuming you're relatively new to imaging(at least with the reflector) and in that case I don't think you'll notice the slighly lesser quality of the baader or the 0.9x compared to the aplanatic.  Though I've never compared the three, so I can't say for sure. But here's what I found in my research:
 

Here's a search for the baader on astrobin.  A lot of good result using setups similar to yours
https://www.astrobin.com/search/?q=Baader MPCC Mk III

And here with the f4 Aplanatic
https://www.astrobin.com/search/?q=SkyWatcher Aplanatic Coma Corrector

And the SW 0.9x
https://www.astrobin.com/search/?q=Skywatcher 0.9x coma corector

If you zoom into the corners, you can see a slight difference in the coma, but I was looking for it, so I couldn't say if someone would notice the difference if they weren't specifically looking for it. 
But if you can afford it, the Aplanatic would seem like the better option
 

Here's the google definition of Aplanatic:
"An aplanatic lens is a lens that is free of both spherical and coma aberrations. Aplanatic lenses can be made by combining two or three lens elements."
In other words, the optical quality is just better.


But to sum up:
The Baader and 0.9x is fine if you're just starting out, but if you can afford the Aplanatic, go for it!

Thanks! I'm not new to imaging at all tbh, I imaged with the Newtonian in the past, I also own a C8 Edge HD and a SharpStar refractor.

I did search for results in astrobin, but I don't think you can really tell how much the image is cropped, so that's why it's hard to determine that.
But that's sooooooo weird though, as I remember searching yesterday and seeing LOTS people saying that the baader is not a good choice, but now all I see are good reviews, maybe I was just too tired? I'll try to go over my previous history and see what I find there.

I don't really have a budget limit, I could afford any of them but obviously, the cheaper the better, especially considering the fact that I plan on replacing it with an Esprit 120 in the future(when prices will be back to normal, so could be months, years, or never haha).

I wonder about a comparison between the baader and the 0.9x, cause faster f ratio(even though it's not by much) is always appealing!

3 minutes ago, rnobleeddy said:

I've used both a baader mpcc mark ii and mark ii with sensors up to and including aps-c and they've performed fine. I'm not the pickiest imager, but I can't see any coma remaining. I know it's used by a few people and I've not heard any particularly bad reviews, but it probably depends how much you stare at the stars in the corners!

I heard from someone I purchased a 2nd hand scope from that the aplanatic cc worked well too. 

Thanks for the comment, I am rather picky I'd say regarding the edges, but that depends on what I use, I don't expect a Newtonian to be as flat as a quality refractor.

One more general question, there seems to be many types of baader coma correctors and it seems like there are some slight differences between them, any 'best' version out there?

Thank you both

Hey, I've read a few previous discussions about it here, but some of them are old, so I just wanted to ask and hear some thoughts.

I have a Skywatcher Explorer 200P (1000mm, F/5) I'm using for imaging along with the ASI071MC pro, and I'd like to get a coma corrector for it.
There seems to be lots of possible options so I'd like to get some suggestions.

These are the common options:
https://www.firstlightoptics.com/coma-correctors/baader-mark-iii-mpcc-coma-corrector-photographic.html
https://www.firstlightoptics.com/coma-correctors/skywatcher-f4-aplanatic-coma-corrector.html
https://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html

As far as I understood - the baader one is very bad and is not recommended, the f4 aplanatic should be great, and the 0.9x coma corrector also seems to be ok, though there is a huge price difference between that and the aplanatic and the question is why?
Is it because it's meant for f/4 which is harder to make? Or is it just higher quality overall? Which one would work better for me? And how flat it is actually?

I don't see any image circle or any other useful information for them, so that kinda makes it hard to understand their quality, and that kinda leaves it to people's experience to 'tell the tale'.

Though I'll be using an APS-C sensor, full frame ability would always be welcomed, of course, other suggestions that I didn't link could work as well.
Thanks for the help

On 10/02/2021 at 17:12, rodrigol said:

Fantastic! Could you please post an image of how you connected the reducer to the camera? 

I don't own the Esprit 120 yet, so sorry can't help with that 😕

On 07/01/2021 at 23:21, Frank_Teunissen said:

I own an “older” Esprit 150ED with the red marks on it. The new dedicated SW reducer 0.77x for the Esprit 150ED won’t fit into drawtube of the focusser. Why doesn’t SkyWatcher warn the users of these Esprit’s?

 

 

Is it possible to replace that to match?

2 minutes ago, kbrown said:

No. I only needed to do it once after I had my modifications ready and assembled. From there on it just re-uses the offsets from the Arduino EEPROM memory. You shouldn't have to touch them even if you open the housing to take out the wheel in order to change filters.

Oh, I thought you were referring to different type of calibrations, 1 for offsets which you do just once, and the other that you do just to get the current position or something in case it's manually moved, but yeah since you have the sensors there's probably no need to that.

Awesome, thanks

40 minutes ago, kbrown said:

The calibration in my case is just a manual/visual process to see where the filter slot stops and whether it needs adjustment. Then yes these adjustments are stored on board 'permanently'. Until you change them again that is. I haven't had to change mine

I can't remember whether uploading a new version of the Arduino code retains the values. Probably not...

So the calibration is just something you're running at the beginning of each session just to initialize the positions or something? Or you don't even need that since you can just know when you reach position x?

And thanks a lot for answering all my questions, it's really helpful.

6 minutes ago, kbrown said:

3D printing threads isn't a problem. I've done it many times. However I would not 3D print the filter wheel housing as it needs to be quite sturdy due to the weight of the camera and other accessories hanging off of it.

Yes the sensors can detect the magnet before it's centred under the sensor. But this is a constant offset as long as the sensors are fixed in place so I take care of this in software. I turn the wheel until I detect the first magnet. Then I turn a little bit more to see if there's any other magnets coming "into view". From here I apply a user defined offset (backwards or forwards) to centre the filter on the optical path. There are two offsets per filter which can vary depending which direction the wheel was turning. These offsets are exposed in the INDI driver and stored in the Arduino's built in EEPROM so the stay there even when not powered. I haven't had to touch these offsets since I did my initial calibration.

You can see this in action here:

 

I did manage to make pretty good 3D printed threads using PETG, which is also very sturdy, but I think I'd always try to avoid that when I have other options, and yeah there's obviously the weight part as well, even though PETG is really strong, maybe just strong enough? Depends on the use case obviously.

And that's great...When you say that you haven't had to touch the offsets since the initial calibration, do you mean that the calibration calculates the offsets and stores them 'permanently'?

25 minutes ago, kbrown said:

Like I mentioned before the fourth isn't used at all. I just put it in just in case as I wasn't sure how the magnets and sensors would play together so close to each other.

Another idea I had in my mind was to 3D print a 9 x 1.25" filter carousel that would fit in the same housing. That would require four sensors. I haven't done this yet though. Don't even know if it would be physically possible

Oh awesome. Sorry, lots of information to process and understand(for me at least :x and I want to precisely understand everything I do)

That sounds like a cool idea, at first I thought of completely 3D printing a filter wheel, but I feel like it just won't be good enough, especially when you have to somehow take care of the threads, and sounds like it won't be an easy task, or at least something that will last for long time.

I think the last question about the magnets is about the usage, I think that the sensor should detect the magnets even before the sensor is exactly above the center of the magnets? How do you handle that? Can it be measured with the hall sensor?

19 minutes ago, kbrown said:

Yes the sensors are aligned so that the magnets on the wheel travel right underneath them. One sensor detects one magnet at a time so basically I encode the slots with the presence or absence of the magnets as seen here:

Notice the variation of the magnet placements on each slot. This is what I tried to explain in my first reply with the truth table. Hope this helps?

Yep that's pretty much what I thought, sorry once again...But why do you need 4 sensors in that case? Since you're using only 3 magnets variations, 3 sensors should be enough for that? Is the 4th sensor used for something else? Or I'm still missing something?

Thanks, that's really really useful.

10 minutes ago, kbrown said:

This photo shows the sensors soldered on the PCB (Click on the arrow icon on the top right to get to the right post). They're the four transistor like devices in the middle with bent legs to get them close to the surface of the wheel housing.

This photo shows the additional bracket I made to hold the screws on top of the sensors.

 

I see, and how do you detect the different positions according the positions of these sensors? By the different magnets bits I guess? And it looks like all the sensors are aligned, does each of them checks for something different?

Sorry, I'm just still missing the basic understanding of that. I'm not in a hurry making that so I really want to plan everything from beginning to end before starting and take my time with it.

6 minutes ago, kbrown said:

Your wheel looks exactly the same I have as far as I can see.

No there's four sensors (U2, U3, U4 and U5 in the schematic. Have another look in my old thread you linked in the first post. There's tons of photos showing how I put everything together. Do you have a CNC mill/router? Not sure if I would have attempted this without mine...

Right, didn't figure that it's the hall sensor in the schematics, but I don't think the photos show where exactly the sensors are positioned on the filter wheel? Or I just missed it?

I also don't have a CNC machine, but I think my tools should be good enough in order to make this according to what I've seen in your build.