Sounds good Michel! ?We will make it happen this Thursday ... and it'll be a good time to start Astro Day planning and ideas!

Cheers!
Pierre

Good idea Pierre see you next Thursday….
BTW Denis and I could not attend last night….
Apologies to those members that might have been present.

Michel

Oh no! ?I can't believe the gabfest escaped me again this month! ? I somehow thought it was not until next week!

So..... any OAOG'ers interested in an impromptu gabfest next week?

Cheers!
- Pierre

OAOG Gabfest

When:
Thursday, March 16, 2023
7:30pm to 10:00pm
(UTC-04:00) America/New York

Where:
Tim Horton's - 1720 Innes Road, Ottawa

View Event

Description:
As there seems to be sufficient interest to meet in person again, I have setup the calendar invite to meet at the Tim Horton's on Innes at Cyrville where we used to meet during the pre-COVID days.

Reminder: OAOG Gabfest

When:
Thursday, March 16, 2023
7:30pm to 10:00pm
(UTC-04:00) America/New York

Where:
Tim Horton's - 1720 Innes Road, Ottawa

View Event

Description:
As there seems to be sufficient interest to meet in person again, I have setup the calendar invite to meet at the Tim Horton's on Innes at Cyrville where we used to meet during the pre-COVID days.

Greetings Everyone!

Another year has come and gone, and so it is time once again to start planning for this year's Astronomy Day.? The event is scheduled for Saturday, April 29th this year with Sunday as a rain date.? With the success we had last year going back to an in-person event, I am keen to do the same again this year.? I am just now getting the ball rolling with planning, so stay tuned for updates.? If you think you might be interested in helping out this year, or would like more information about the event, please feel free to contact me.? You can find more information on the event at our event website:? .

I am looking forward to seeing everyone out for another great Astronomy Day!

Cheers,

Jim Thompson

Hey all,

I'm a purely visual observer. I have an old 127mm ES triplet. It's about 15 years old made with whatever glass was used back then.
It shows some chromatic aberation around the moon. It's not great, but tolerable.

Now, the focuser on it is not up to the task of holding my binoviewers and herschel wedge and upgrading it isn't on the table without cutting the tube, which I'm not really keen about.

My question revolves around the more exotic glass that is now found in the same class of scopes. FCD100,FL55,53, etc. If Im purely sticking to visual, would you go with a really good modern doublet, or still a triplet. Could I expect equal or better performance with modern premium doublets/triplets over what I currently have? Could I get equal or bettery performance with a modern doublet? Understanding that there are more parameters than jsut the glass used, but how it was shaped, collimation, etc.

I'd like to buy a? new scope that natively supports binovieweing without barlows/correctors, and am trying to decide whether to go with the doublet/triplet fomr Telescope Service/WO <insert your recommendation here>

If anyone in the Ottawa area has a premium doublet or triplet, I'd love to take a look through it. I can offer an ES127mm or Coronado 90mm double stack to try out as well.

I very much agree! ?This is great information Jim! ?Your post is well appreciated!

Cheers!

- Pierre

开云体育

What a great response Jim we all benefitted from it. Thank you.

Bojan, Jim,

Thanks for your very helpful replies.? That's the kind of information that i was looking for and i appreciate you taking the time to share it with me.

Have a great day,

Take care and stay safe,

Peter Fundarek

Hi Peter,

You are not alone in your desire to view nebulae from within the borders of the Ottawa area.? There are a number of OAOG members, including myself, who observe from our urban backyards using a camera.? The ability to observe using a camera is greatly enhanced by adding a carefully selected filter, to the extent that I feel there are practically no limitations to what I can observe from my backyard.? I have laid out some discussion points below that will hopefully get you going.

1. Halpha vs. O-III vs. Hbeta:? Visual observers are taught to use O-III filters to improve contrast on nebulae.? This is because that particular emission is well placed in the range of wavelengths the human eye is sensitive to when dark adapted, ~496-501nm.? O-III filters work well visually as long as the target emits some O-III, but some nebulae do not.? One example is the Horsehead Nebula which is entirely emission from Hydrogen.? That is why visual observers are advised to try an Hbeta filter when trying to see the Horsehead or other faint HII-type emission nebulae.? The Hbeta emission is at ~486nm, so still well placed for our dark adapted human eyes.? The reality however is that BY FAR the largest emission from nebulae comes from Halpha at 656nm.? Our eyes can't see this wavelength when dark adapted, but your camera can.? You are much better off focusing your attention on Halpha for faint nebulae.? O-III is still important when using a camera, but mostly when observing planetary nebulae or supernova remnants which tend to be strong in both emissions.

2. UHC filters:? The performance of different brand UHC filters varies widely as there is no industry standard for what "UHC" means.? They are all made specifically for visual observing, therefore they are not necessarily well suited for use with a camera.? To be an effective filter for use with a camera the filter needs to pass Halpha at 656nm.? Because human eyes can't see that wavelength when dark adapted, most UHC filters do not pass Halpha.? I have researched and tested many UHC filters, and the only ones I recommend for use with a camera are:? Astronomik UHC, Optolong UHC, and Arcturus Narrow.? The Astronomik UHC is my top recommendation because it also passes near infrared, which makes the filter effective on galaxies as well.? If your UHC filter is not one of the three I mention above, it is likely not well suited for use with your camera.

3.? Filters & Exposure Time:? I have been researching filters for use with cameras for more than 10 years, and one universal truth that has been proven time and again is that the narrower the pass bands of your filter are, the larger the increase in contrast.? This increase in contrast comes however at the cost of longer exposure times.? Because adding a filter blocks light from entering the camera (mostly light pollution, but light nonetheless), the resulting image will be darker.? One can choose to keep their exposure time the same when adding a filter, and simply stretch the histogram to brighten the image, but that method tends to result in a noisy image and does not take full advantage of the filter.? In my testing I have found that the exposure time required for a particular filter relative to no filter is inversely proportional to a measurable parameter called the Luminous Transmissivity or %LT.? This parameter is a single number that indicates generally what percentage of the incoming light is getting through the filter.? So for example the Astronomik UHC has a %LT value of 36%, therefore one would expect their exposure time to be (0.36^-1) 2.8x longer using the UHC than if they had no filter.? With that increase in exposure time however comes a 3.1x increase in nebula contrast.? So, where am I going with this?? Well it leads to the reality that you will be limited on how narrow a filter you are able to use based on how well your telescope is able to track your target.? I have a 10" scope operating around f/6.5, and my pier mounted GEM mount is able to give me about 45 to 60 seconds of good tracking at that focal length.? Anything longer than that and I would need guiding.? In my experience, a DS10C binned 2x2 should be fine with filters down to 5 to 7nm wide on this setup.? On my portable alt-az mount however, I can only get maybe 20-30sec of good tracking at that focal length so filters as narrow as 5 to 7nm would be too narrow for that setup.? I tend to use short focal length refractors only on my alt-az mount so the tracking time does not limit me on how narrow a filter I use.? A question then for you Peter is how long a sub-exposure can you reliably achieve with your C11 and DS10C?? The answer will help direct you to the right filter for your application.

4.? Multi-Narrowband vs. Single Narrowband:? I agree with Bojan that an Halpha narrowband filter is the best filter for emission nebulae.? However the caveat is that you should be using this filter with a monochrome camera.? If you try to use it with a colour camera you will only be getting signal on one out of four pixels which is a big hit on the resolution of your image.? Since you noted in your original post that you have a colour camera, I would recommend you don't use an Halpha filter, but instead use a multi-narrowband.? These filters also go by the name dual-band, tri-band, etc, but they are essentially all in the same family of filters that have narrow pass bands around the Hbeta-OIII group of emissions and the Halpha-NII-SII group of emissions.? There are now numerous offerings available, all of which I have tested over the past couple of years.? If you are having trouble sleeping you can read through my various test reports on these filters:



To save you some time, my recommended filters, in order of decreasing band width are:

IDAS NBZ (12nm)
Optolong L-eXtreme (7nm)
Antlia ALP-T (5nm)
Optolong L-uLtimate (3nm)

I currently use the L-uLtimate filter from my backyard in central Ottawa with good results, but I am using 30 to 60sec sub-exposures on an f/5 scope.? Several in our group use the NBZ filter with good success as the burden on exposure time is much less than the narrower filters.? There is also a cost premium associated with narrower filters, so between your mount tracking capability and the amount of money you are willing to spend, the best filter for you is somewhere between these two extremes.

Cheers,

Jim Thompson

Morning.

Both of those objects are rich in H-alpha, and probably less so in OIII and H-beta.

In order to have a chance of seeing them with the highest possible contrast, you'll need a H-alpha filter.

The L-extreme (and other dual/tri band pass filters) will pass through more light at other wavelengths which will reduce contrast away from h-alpha.

If you're working with high light pollution you want to maximize contrast for an h-alpha object, only pass through h-alpha light at a bandpass that you can handle with your camera. I have 3nm chromas which work very well but 5-7nm should work as too.

Hello, everyone.? ?It's been a while since i posted here but I have been keeping an eye on the messages.? ?

I observe from my backyard in Orleans and the skies are pretty good to the south (my main viewing) despite the Walmart nearby.? ?I'd like to have a look at the Flame Nebula and maybe the Horsehead but when I checked both, I couldn't readily see them with my setup (C11 Edge with Mallincam DSC10C camera, 0.7 focal reducer).? ?I tried both my OIII and UHC filters to no avail.? ?I was thinking that I needed something with H-alpha and maybe H-beta and saw that the Optoplong L--ENhance filter has those wavelengths covered.? But then reviews suggested that the L-EXtreme was better, although it doesn't cover the H-beta wavelengths as much.? ?Based on my equipment and likely targets, i would welcome any suggestions as to which of these (or some other filter) would be the best choice.??

Any help would be appreciated.

Clear skies, everyone.

Take care and stay safe,

Peter Fundarek

OAOG Gabfest

When:
Thursday, February 16, 2023
7:30pm to 10:00pm
(UTC-05:00) America/New York

Where:
Tim Horton's - 1720 Innes Road, Ottawa

View Event

Description:
As there seems to be sufficient interest to meet in person again, I have setup the calendar invite to meet at the Tim Horton's on Innes at Cyrville where we used to meet during the pre-COVID days.

Reminder: OAOG Gabfest

When:
Thursday, February 16, 2023
7:30pm to 10:00pm
(UTC-05:00) America/New York

Where:
Tim Horton's - 1720 Innes Road, Ottawa

View Event

Description:
As there seems to be sufficient interest to meet in person again, I have setup the calendar invite to meet at the Tim Horton's on Innes at Cyrville where we used to meet during the pre-COVID days.

OAOG Gabfest

When:
Thursday, January 19, 2023
7:30pm to 10:00pm
(UTC-05:00) America/New York

Where:
Tim Horton's - 1720 Innes Road, Ottawa

View Event

Description:
As there seems to be sufficient interest to meet in person again, I have setup the calendar invite to meet at the Tim Horton's on Innes at Cyrville where we used to meet during the pre-COVID days.

A number of OAOG members have confirmed so tonight’s gabfest is a GO! ?:))

Everyone is welcome.

Clear skies,
Pierre

Hello all,

It would be great to get together tonight for the gabfest as it's been a while.

Cheers!

- Pierre

Reminder: OAOG Gabfest

When:
Thursday, January 19, 2023
7:30pm to 10:00pm
(UTC-05:00) America/New York

Where:
Tim Horton's - 1720 Innes Road, Ottawa

View Event

Description:
As there seems to be sufficient interest to meet in person again, I have setup the calendar invite to meet at the Tim Horton's on Innes at Cyrville where we used to meet during the pre-COVID days.

Hi Andrea,

The Antlia RGB Ultra is a brand new filter that is touted as being able to provide improved views of reflection nebulae and galaxies, as well as emission nebulae.?



It is apparently able to achieve this magical feat by having three distinct pass bands:? one at Halpha (656nm), one at O-III (500nm), and one in the blue part of the spectrum (430nm).? Given my experience testing many types of filters under light polluted skies, I was skeptical about the filter and decided to buy one to try.? The M42 comparison images at the front of my Flickr folder are from the first test I did, evaluating how the RGB Ultra performs compared to a range of other typical filters.? The RGB Ultra performed pretty much as I was expecting:? slightly more contrast on the emission nebulae part of M42 than the UV/IR cut and IDAS LPS-D2, but not any significant improvement on the reflection part of the Running Man.? Unfortunately I don't think there is a silver bullet filter that improves contrast on reflection nebulae under light polluted skies.? Reflection nebulae emit over too broad a wavelength range to be effectively isolated from light pollution.? I may do a couple more tests with the filter, such as on a galaxy for completeness, but otherwise I think the filter's journey is done.? I am waiting however for another new filter to come in from Astro Hutech that has more potential.? It is essentially an IDAS NBZ but it also has a pass band in the near infrared part of the spectrum.? The filter is called the Galaxy & Nebula Booster, and I think it has the potential to work very well.? A prototype has already been tested by Cuiv the Lazy Geek on his Youtube channel.? He lives in Tokyo and so has more direct access to new products coming out of IDAS which is situated in Japan.? If you are interested, I will keep you informed of how things go with the GNB filter.

Cheers,

Jim T.