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10" Flextube goes camping

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#1 Eddgie

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Posted 15 October 2020 - 12:23 PM

I posted a few pictures in the imaging post, but just a brief report on my first camping trip with the Flextube.  Inks Lake State park is was reading 20.9 on the SQM-L but there was a considerable amount of dust in the air during the day and I could tell using the naked eye that the Milky Way was a bit subdued, so clearly the transparency was a bit low. 

 

 

The detents and the ASA focal reducer worked great. I only did image intensifier (did not bring the binoviewers because I can do planets from home).

 

Overall, the visual views were quite excellent.   While the fully illuminated circle is very small, the falloff is subtle. View were sharp right to the edge and only when imaging with narrow band filters was the falloff more noticeable but even here, that depended on the exposure time. 

 

The 875mm focal lenght offers twice the scale of my 6" f/2.8 and but with considerably better limiting magnitude, so sweeping down the walls of the great rift was a constant rich field experience, but at the same time, the dark nebula along the walls has so much scale that it is not something that I found as enjoyable in the 10" f/3.44 as with the 6" f/2.8 and frankly, one of my favorite tools for the large scale structure remain the Mod 3 binocular at 3x.  Still, trip down then up the walls of the rift was quite lovely. 

 

Ink Spot was disappointing. I suspect this was due to the reduced transparency, but some to image scale as well.  I could see it but it was not the dark black that I typically see from dark skies.  

 

Nebula like the Lagoon pretty much fit entirely into the field, but NA and Pelican were far to large, though the scale made study of the structure much better than in the 6". 

 

Lots of globulars but I did not do the native 1200mm focal length and I think that lenght would have been better, and I also have a barlow element in my filter wheel so I could have eked out about 1800mm of focal lenght with that setup, but I simply just did not bother swapping it over. I see the Flextube going to 1200mm mostly during galaxy season

 

Camp sites are close at Inks Lake and there was an annoying flicker from neighbor camp fires when pointing ins some directions and even some light leaking into the slot in the side of the filter wheel where the edge of the wheel sticks out. I need to remedy that somehow.

 

For visual, the illumination falloff is very subtle but with the H-a filters and longer exposures, the illumination falloff is more easily visible, but my primary use of my telescope and image intensifier is real time viewing, so I only do an occasional picture to share, but here, the purpose it so show the illumination characteristics of the Felextube when used at the -25mm custom detent position, which a quite happy with. Again, for visual, I found the illumination falloff the be very subtle due to the small 18mm image circle we use.

 

This is a 1/2 second exposure.  ISO is 1000 with the Galaxy S9 phone working at f/1.5.  I typically do not spend any time playing with manual exposure trusting the phone camera to take care of that.  I use night vision mode and I suspect that it is perhaps coupling pixels or something because the resolution seems lower than when I use Pro mode, but the exposure times in Pro mode have to be much longer.  I just hate imaging. What can I say...

 

Swan nebula

 

swan 70.jpg

 

The purpose of the post though was to convey my experience with the 10" Flextube and while I still very unhappy about what it took to make the scope serviceable and as just a telescope I don't think I would have been as happy as I would have been with maybe the Apertura 10", but as a do-it-all platform, it has indeed worked exceptionally well for me.  I could never have fit my 12" dob into the SUV and still had room for the 70" television (only kidding but if you saw our loadout you would think there must be on in there somewhere). The 10" had a footprint that was no larger than the 6" on the IOptron Az Mount Pro, and smaller than the 8" on the Az Mount Pro, so a home run in terms of getting a decent size aperture in a space that is small enough to still bring camping.  I feel like in spite of my issues with the base and balance, it was the best telescope for me and my range of viewing interests.

 

Hope everyone is having an excellent day!


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#2 Eddgie

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Posted 15 October 2020 - 12:30 PM

Same exposure but I think this one shows the field illumination falloff a bit better because there is a lot of nebula around the Trifid.

 

Trifed 70.jpg


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#3 GeezerGazer

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Posted 15 October 2020 - 04:02 PM

Overall, it sounds like the 10" Flextube is a good fit for you.  Excellent report and great images Ed.  

 

Last night, I was out observing for the first time in months.  Seeing was excellent but transparency was way off because of ash still floating around with each little breeze that comes up.  It's hard to imagine how many gazillion tons of ash have fallen here in CA since the fires began in late July.  I had to clean everything today; it all had a thick coating of ash-dust.  

 

All visual for me last night; had a great image of Mars, Jupiter, Saturn, Uranus and Neptune with a 140 apo at 245x.  Couldn't confirm Pluto, just too small and faint, but NEXUS said I was in the right place.  Checked a few doubles.  Then switched to NV for an hour.  It was really good to be under the stars again! 

 

I stayed at Inks Lakes one night a long time ago when I bicycled the Hill Country.  Pedernales Falls one night too.  It was in the Spring when the bluebells and paint brush were in bloom.  It's really a great part of Texas.  

Ray


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#4 Eddgie

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Posted 15 October 2020 - 04:41 PM

 

 Pedernales Falls one night too. 

I have been to Perdenales to observe but never to camp.  I am hoping to get out there in the next week to check the campgrounds and maybe camp there during the next new moon.

 

Sadly, it has been brutally dusty here in the last week and a half. No rain for almost six weeks and this is our rainy season. 


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#5 Baatar

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Posted 17 October 2020 - 01:52 AM

Eddgie, nice camping and photos. Wow, photos help and speak thousands words.

With your NV talks you are luring me into the NV. And your photos are just speeding up the process. Did some quick reading and am still not getting a good grip on the subject. Two quick questions if you can get me started:

1. I may not go to dark sites often. Being in the city I am in Bortle 6-ish sky. Is it still worth doing NV comparing what I may get from NV with what it would cost? I assume it is not a cheap undertaking.

EDIT: ok, just read some other posts, and NV really helps even in red zone.

2. You pretty much know my equipment, and with a few eyepieces I have (in my sig), what you suggest I need to get to get started, or absolutely "must haves" in NV astronomy?

EDIT: I mean, there are many options and choices. Say, what would be optimal to start with a modest budget of under 1000. I was thinking of getting a few APM 100 degree eyepieces for mono viewing, I may just spend that money into NV.

Appreciate any advice.

Want to maximize my enjoynent from this hobby.

.

Edited by Baatar, 17 October 2020 - 02:43 AM.


#6 gatorengineer

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Posted 17 October 2020 - 08:45 AM

I live in an orange red zone, and have seen more with my 80mm NV spyglass, than ever before........ it gave me the hobby back....  IMHO opinon best money ever spent on the hobby - 

 

First Decision Mod3C (Prime) or Afocal.  I went Afocal with no regrets most here are prime.  See mike lockwoods NV page for a wealth of info.

 

Essentials for Afocal

 

3-3.5nm HA filter (Budget Antilia or baader HS 3, high end Chroma or Astrodon)

Light Pollution Block filter for non nebula

Wide EPs - for me Siebert 36 Russell Plossls 45,50, 56, and 65  most here seem to use the TV 55/67  (I bought the 50 first but if I had planned better would have skipped this one)



#7 Eddgie

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Posted 17 October 2020 - 09:39 AM


EDIT: I mean, there are many options and choices. Say, what would be optimal to start with a modest budget of under 1000. I was thinking of getting a few APM 100 degree eyepieces for mono viewing, I may just spend that money into NV.



.

Hey Baatar,

 

Sadly, there is not going to be much available at your price point and it is much more expensive in EU than US.  Even in the US, a good entry level device like a used Micro Monocular will sell for $1800 or so and again, in EU, much more.

 

CN Member Joko is a dealer for NV in EU.   Again, I think your budget will prevent you from doing very much, but you should touch base with him.  Maybe he can keep his eye open for something, but I think to get anything worth getting, you would need to considerably increase your budget.

 

So sorry.  NV Is great, but it is not cheap to do. 



#8 Baatar

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Posted 17 October 2020 - 02:57 PM

Hi Eddgie, gatorengineer,

Thanks for your replies. Ok, I get it I will need to significantly up my budget. Am not going to give up, I will forget about APM 100s and will start saving.

Unfortunately, the budget is not the biggest issues, availability is always a problem in EU. Will check with Joko to hear what he says.

.

#9 Eddgie

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Posted 17 October 2020 - 04:20 PM

Hi Eddgie, gatorengineer,

Thanks for your replies. Ok, I get it I will need to significantly up my budget. Am not going to give up, I will forget about APM 100s and will start saving.

Unfortunately, the budget is not the biggest issues, availability is always a problem in EU. Will check with Joko to hear what he says.

 

Well, there are plenty of options if you have the budget. Photonis and Hardin both are EU based and both make excellent tubes. Past that, and it is just a budget issue. 



#10 a__l

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Posted 17 October 2020 - 06:08 PM

Ray, the current version of Nexus has problems with planets (my version is 1.3.7 2019.06.10). For planets, I use Telrad.

 

gatorengineer, this is not true. Afocal limits your ability to use NV. Alternatively, a lot of unnecessary glass is used to achieve your goals. I see the need to use afocal for only one purpose, the maximum field with TV67. But at the same time, the problems of the NV lens are additionally visible (Envis too). 

 

Flextube, I understand correctly that this is Newton with ASA corrector using prime focus? Have you compared this corrector with Paracorr-2? Do I understand correctly that it differs only in the absence of a barlow effect?


Edited by a__l, 17 October 2020 - 07:14 PM.

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#11 gatorengineer

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Posted 17 October 2020 - 07:40 PM

Havent seen Afocal so I cant comment, but very happy with what I have, with Afocal, I can go alot faster than prime focus......  

 

Been very interested in the 0.75x correctors.......but I dont think we have any users here



#12 a__l

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Posted 17 October 2020 - 08:02 PM

Yes it is. 67 TV especially with narrow band filters. But with prime focus you will increase the image size. With narrow-band filters, the brightness remains acceptable, it works well for galaxies (without any filters). Anyway for f/4.


Edited by a__l, 17 October 2020 - 09:08 PM.


#13 Eddgie

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Posted 17 October 2020 - 10:09 PM

Ray, the current version of Nexus has problems with planets (my version is 1.3.7 2019.06.10). For planets, I use Telrad.

 

gatorengineer, this is not true. Afocal limits your ability to use NV. Alternatively, a lot of unnecessary glass is used to achieve your goals. I see the need to use afocal for only one purpose, the maximum field with TV67. But at the same time, the problems of the NV lens are additionally visible (Envis too). 

 

Flextube, I understand correctly that this is Newton with ASA corrector using prime focus? Have you compared this corrector with Paracorr-2? Do I understand correctly that it differs only in the absence of a barlow effect?

The Sky-Watcher Flextube itself is a 10" f/4.7 telescope but because it has adjustable trusses, you can shorten the trusses enough so that you can use focal reducers.  The ASA unit I use is a .73 reducer and coma corrector.  Because the focal reducer needs 65mm of spacing, you really need a telescope with 90mm of back focus for it to work, but since the Flextube lets you adjust the back focus, by shortening the trusses, you can shorten them (25mm in my case) and this turns the telescope into an f/3.44 scope, though when you do this, you also reduce the fully illuminated field size, so rather than maybe an 8mm fully illuminated circle, with the trusses shortened and the reducer in place, the fully illuminated field is only maybe 2mm or 3mm, but the falloff is not enough to really notice (does not look vignetted). 

 

My own preference is to work at prime focus and since the focal reducer requires 65mm or so of spacing, this leaves enough room for a filter wheel. One of my filter wheel positions has a Barlow in it and of course If I want higher power than that, I can use the MPCC to make the device back to 1200mm and then the built in Barlow gives me another bump in effective focal lenght to maybe 1800mm.



#14 Baatar

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Posted 18 October 2020 - 12:17 AM

My own preference is to work at prime focus and since the focal reducer requires 65mm or so of spacing, this leaves enough room for a filter wheel. One of my filter wheel positions has a Barlow in it and of course If I want higher power than that, I can use the MPCC to make the device back to 1200mm and then the built in Barlow gives me another bump in effective focal lenght to maybe 1800mm.


Eddgie,

I wrote to Joko, am waiting for reply. I thought about NV idea overnight and if I really need to go down that route. If I do, I feel it may be better if I just try to replicate your setup. We have same scopes, and I know it works for you.

Your photos are imprinted in my mind and will never leave, and I would not want anything less now. If I will have to up the budget I am willing to do that, especially for the amount of money, I want to pay once and not to regret later. I saw other photos in the top thread of this NV forum, and really like and prefer your setup's rendition and presentation. The hook is set deep.

Could you please run down the things you are using and in what sequence? ASA reducer, a filter and which NV device? I am not sure if I need a filter wheel and many filters, unless absolutely necessary. What is the one you use most, and basically to have the same view as in your photos? Regarding ASA reducer/corrector, it is available from Telescope Service, and which adapter I need?

Regarding eyepieces, does it have to be very long focal length one, like over 50mm? What about APM 30mm or ES68/24mm I have? I get it the wider is better, but is it necessary to go beyond what I have? Sorry for many newbie questions, the NV astronomy is completely alien to me.

Once I know what to get, then it is just a question where and how to get them.

.

Edited by Baatar, 18 October 2020 - 12:59 AM.


#15 Baatar

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Posted 18 October 2020 - 06:41 AM

Jonathan,

Thanks, will wait for your PM. And will explore your links with great interest.

Cheers,

.

#16 gatorengineer

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Posted 18 October 2020 - 07:03 AM

Eddgie - What percentage of the time do you spend over 1m FL?   I find most of my time wishing for more field not less.......



#17 Joko

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Posted 18 October 2020 - 07:37 AM

Jonathan,

Thanks, will wait for your PM. And will explore your links with great interest.

Cheers,

.

PM sent.



#18 Eddgie

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Posted 18 October 2020 - 01:37 PM


Could you please run down the things you are using and in what sequence? ASA reducer, a filter and which NV device? I am not sure if I need a filter wheel and many filters, unless absolutely necessary. What is the one you use most, and basically to have the same view as in your photos? Regarding ASA reducer/corrector, it is available from Telescope Service, and which adapter I need?

Regarding eyepieces, does it have to be very long focal length one, like over 50mm? What about APM 30mm or ES68/24mm I have? I get it the wider is better, but is it necessary to go beyond what I have? Sorry for many newbie questions, the NV astronomy is completely alien to me.

Once I know what to get, then it is just a question where and how to get them.

.

For the picture above, I was using the 10" at the custom detent position but I will say that if you are going to use the binoviewer with a 1.7x GPC as well, and you think about doing a custom detent and you are going to use the scope for planets with a 1.7x GPC I would go more than 25mm even if there is a slight aperture loss.  The reason is because while I can reach focus with the Binoviewer and 1.7x GPC at the same detent position as I am using for NV, at this position, the focuser tube sticks into the light path.  By moving the detent down 35mm, you would be slighly below full aperture for NV but so close that you would not be able to see the difference and you would get the focuser tube out of the light path.

 

The other option would be to buy the Skywatcher low profile focuser.  For some odd reason, no one in the US sells this focuser, but I see it being sold in EU.   This focuser would keep the focuser tube from sticking into the light path.

 

But I digress.  I was using the custom 25mm detent.

 

I am using a Mod 3, but Joko has a C mount device that would have similar characteristics, but you would have to check with him for exact figures.

 

I am using the ASA Reducer/Corrector from the Boren Simon 6" f/4. This was from Telescope express.   I do not see the exact model as the one sold with the Boren Simon shown on their web site but I am sure that they could tell you the model number.

 

Next, I am using a spacer between the corrector and my filter wheel.  The corrector used T2 thread as does the filter wheel, so you just need to select a spacer that has the right length to make the total light path to the photocatode 65mm.

 

Next is my filter wheel.  I have an empty space, a 650nm long pass filter, a 12nm H-a filter, a 6nm H-a filter, and in one position I have a Barlow lens.  Now at f/3.44, the edge is not sharp, but it is nice to have a little extra amplification.  I think it probably works out to about 1.5x. 

 

Since the rear of my filter wheel is T2 Female, I use a T2 gender changer to convert it to T2 male.  I have a T2 to C mount on the device, though I think the device Joko sells has native T2 thread, so you might not need this.

 

Then the device.

 

reducer.jpg

 

A note. My spacing is not exact.  If you were using a super high megapixel camera and a long exposure you would want the spacing within a millimeter, but for our application that may not be possible and unless you get more than a couple of millimeters off, it is going to work quite well.

 

If your device uses a native T2 thread, you could eliminate the adapter but you would still need the gender changer.  Because you no longer have the adapter, you might need to use a longer spacer between the filter wheel and the reducer but you want to keep the device as close to the filter wheel as possible to reduce vignetting from the 1.25" filters.  At f/3.44 this is not an issue, but in my 6" f/2.8 it is, but still, for best result, it is probably best to put the device as close to the filter wheel as possible.

 

I also have an MPCC setup so I can work at f/4.7.  I use the same filter wheel and connections on the back side but a different spacer between the MPCC and filter wheel.   Joko could tell you the photocatode distance behind the interface and you would just add the connections and filter wheel thickness to see how much spacer you need.  Anyway, I can change back and forth between the MPCC and the reducer buy just threading on front end off and the other on.  I have some 2" extensions on the front of my MPCC so I can slip it out in the focuser and not have to change the extension on the trusses. 

 

Again, what I am using would probably be a little different than what you would use, but it is just a matter of getting the correct spacing and at f/3.44, I would recommend that this spacing be done on the telescope side of the filter wheel between the filter and the optic (reducer or MPCC) so the actual spacer you will need will probably be a bit different than the one I use.  I think his housing may be a bit better than the Mod 3 actually because if I am not mistaken it has the T2 interface and I think this is a better interface because the T2 is one of the most used interfaces out there. 



#19 Eddgie

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Posted 18 October 2020 - 01:40 PM

And here is the MPCC setup.  Now shown are the 2" extensions. I think I have two for total of 51mm of added extension.  This means that if the focus does not rack out far enough (and it dies not at the modified detent) I can simply pull the whole device out an inch from the focuser and still have plenty of support.

 

20190925_104957 - Copy.jpg

 

 



#20 Eddgie

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Posted 18 October 2020 - 01:51 PM

Eddgie - What percentage of the time do you spend over 1m FL?   I find most of my time wishing for more field not less.......

For now, I only have two telescopes.  The 10" Flextube dob can work at 875mm with the reducer or at 1200mm with the MPCC, and I have a 1.5x Barlow in the filter wheel that will give me an extra 1.5x in either of these positions, though at f/3.44, the edge is not sharp when using the built in Barlow, but it is fine for getting a quick bump in scale for objects at the center of the field.  

 

I also have the Boren Simon.  It is 6" f/2.8 or f/4 and once again, I have the Barlow in the filter wheel. The 6" at f/2.8 gives a 2.4 degree true field.

 

I have a 180mm Nikkor f/2.8 ED lens for larger objects like the California Nebula or North American, and I have the 3x binocular to the really big stuff like Barnard's Loop.

 

Mostly I use the Boren Simon at very dark skies because it excels at doing nebula, but it lacks image scale for glaxies and such.  That is going to be the role of the 10".  

 

So, my primary NV telescope at this point in time is the 10" Sky-Watcher with the 6" as my RFT NV scope.  Fantastic under dark skies..

 

6" Under Bortle 5 skies.  I think this was a 1/2 second exposure at ISO 200 and f/1.5 using my Galaxy phone.  Ink Spot.

 

Ink Spot 75.jpg

 

And the camera can't really resolve out all of the stars visible to the eye.  What appears to be noise or grain in this picture is actually stars.  I estimate 3000 of them.  


Edited by Eddgie, 18 October 2020 - 01:52 PM.


#21 gatorengineer

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Posted 18 October 2020 - 07:08 PM

Thanks Eddgie, 

 

I havent noticed much improvement on Galaxies or clusters with NV, a little better but not much using either the 610 or 685 filters......  With Afocal your Boren can go alot wider than 2.4.  I can get away with a focal reduced 56 plossl in my MN74, for 4.5 degrees, and fitting in some of these bigger gas clouds is an amazing view...  Seing the Lagoon for the first time with NV blew me away.

 

I am liking the 180Ed Nikkor but I am sticking an afocal 45 plossl in it for what calculates to a 10 degree field of view, will probably chase after Precise parts for a formal adapter......  Come to the Afocal Darkside, we have cookies....



#22 Eddgie

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Posted 18 October 2020 - 08:32 PM

Thanks Eddgie, 

 

I havent noticed much improvement on Galaxies or clusters with NV, a little better but not much using either the 610 or 685 filters......  With Afocal your Boren can go alot wider than 2.4.  I can get away with a focal reduced 56 plossl in my MN74, for 4.5 degrees, and fitting in some of these bigger gas clouds is an amazing view...  Seing the Lagoon for the first time with NV blew me away.

 

I am liking the 180Ed Nikkor but I am sticking an afocal 45 plossl in it for what calculates to a 10 degree field of view, will probably chase after Precise parts for a formal adapter......  Come to the Afocal Darkside, we have cookies....

The edge performance is horrible using a 55mm Plossl. 

 

I have done afocal but I just prefer prime focus for a variety of reasons. 



#23 Baatar

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Posted 19 October 2020 - 04:33 AM

Thanks Eddgie for taking your time and posting such a detailed explanation as usual.

 

I would really need to go through your post several times to understand and to digest it.  Your setup appears to be different from Joko's OVNI equipment, which I also need to go through carefully.

 

@Joko, thanks for your PM too.

 

.


Edited by Baatar, 19 October 2020 - 09:07 AM.


#24 Eddgie

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Posted 19 October 2020 - 08:19 AM

Yes, the devices are very different, but in the end, the configuration will likely be very similar with reducer or coma corrector in front of the filter wheel, some amount of spacing between it and the filter wheel, the filter wheel itself, and then the device. 

 

Trust me, it sounds far more complex than it really is. 

 

 

You can also do afocal as well, so lots of options. 


Edited by Eddgie, 19 October 2020 - 08:21 AM.

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#25 RedzoneMN

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Posted 19 October 2020 - 07:29 PM

I live in an orange red zone, and have seen more with my 80mm NV spyglass, than ever before........ it gave me the hobby back....  IMHO opinon best money ever spent on the hobby - 

 

First Decision Mod3C (Prime) or Afocal.  I went Afocal with no regrets most here are prime.  See mike lockwoods NV page for a wealth of info.

 

Essentials for Afocal

 

3-3.5nm HA filter (Budget Antilia or baader HS 3, high end Chroma or Astrodon)

Light Pollution Block filter for non nebula

Wide EPs - for me Siebert 36 Russell Plossls 45,50, 56, and 65  most here seem to use the TV 55/67  (I bought the 50 first but if I had planned better would have skipped this one)

What are the advantages of the Siebert Plossls compared to the TV 55/67 for afocal. I see that the cost is a big one. 




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