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Could this work for EAA

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#1 Bill05

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Posted 09 February 2021 - 03:10 PM

I am interested in EAA, I know next to nothing about it yet, but have started reading, so my wife can "see" DSO's.  Due to some eye issues it is very difficult for her to look thru an eye piece. I am on a limited budget, about $3500 until she knows this works for her.  she originally wanted to use a 12" Dobsonian, which wasn't going to work out so well.

Now we are looking at the Orion Atlas 10 EQ-G goto reflector telescope and either the ASI224MC or the ASI178MC. I will be using a large monitor or TV for her to watch.

If this will work, what accessories and software might I need? if not, what recommendations could  we look at next?

I will keep reading, Very interesting.

We had a couple of small cheap scopes over 10 years ago and remember very little about them.

most viewing will be from the back yard and some traveling to nearby dark locations in southern WA.

 



#2 GazingOli

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Posted 09 February 2021 - 03:30 PM

You will not need so much aperture for EAA. Have a look at some of the recorded EAA sessions to see what you can get, say with a C8 and an ASI533 camera. In the beginnings of the videos the guys  usually present their equipment. 

 

CS.Oli


Edited by GazingOli, 09 February 2021 - 03:39 PM.


#3 GoFish

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Posted 09 February 2021 - 03:49 PM

Hi, bill05

 

First, I like the choice of mount. You could get by, also, with the Sirius EQ-G for EAA. The disadvantage of the Atlas, aside from costing a little more, is that it is a beast to carry and hoist up onto the tripod. But if traditional astrophotography is in your future then the Atlas is the better choice. 

 

Next, I don’t care for the choice of telescope. You can do EAA with a much more manageable OTA than a 10” Newtonian. Instead, I would give very strong consideration to a 6” f/5 Newt. For the price, I think the Celestron OMNI XLT 150 is hard to beat for EAA. But if the budget permits, I would look at the carbon fiber 6” f/5 scopes that Teleskop Services sells. 

 

An ED refractor, 4” f/7 or thereabouts, would be a good choice, too. 

 

A traditional 8” SCT or 6” SCT isn’t a bad choice, either, when paired with the f/6.3 reducer.  The focal length is a little long on the 8” for EAA, but you can do something called “binning” with your camera to partially compensate. 

 

The Sirius mount would handle any of the above scopes for EAA. 

 

Lastly, I would urge you to go big on the camera. Something along the lines of a ZWO ASI294MC (cooled) is where you should start. There are many good choices, albeit pricey, in this class of camera. But the sensor size on the ASI224MC is really too small to allow you to find things, and won’t support wide field views. The ASI178 is slightly better, but you will never regret having a large, cooled sensor for EAA. 

 

 

 



#4 burb scope

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Posted 09 February 2021 - 03:52 PM

I read the book "Video Astronomy on the Go (Using Video Cameras With Small Telescopes)" before I bought my Revolution 2 Imager.

It gave me a lot of background information, and a fair expectation of what to expect.  Published in 2017 it is a little dated, but still gives good relevant information.



#5 Barkingsteve

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Posted 09 February 2021 - 05:27 PM

Firstly the camera, the 533mc pro is a good camera for EAA and a decent sensor size. Cooling will allow you to have a master dark library, which is handy. Software, most people here use sharpcap pro for a reason. It is very good and not too expensive and you can get plenty of advice here.

Mount, unless you plan to do longer exposures ( 20+ seconds ) then an alt/az mount will be easier to setup and use, something like the ioptron AZ mount pro. If you are planning for longer exposures at some point then yes, get an EQ mount. I started out 3 years ago with a celestron evolution mount and while easy to use and did serve me well, after it failed a month ago i finally got myself my first EQ mount, i am still considering getting the ioptron AZ mount for ease of use and quick 'spur of the moment' sessions.

telescope, i have used a small 60mm F/4.5 refractor, a 130mm F/5 reflector and a C925 for EAA, my most used telescope for EAA is the 130mm F/5 by far. If you are not put off by collimation then i would look for an F/4-F/5 150mm-200mm newtonian. These telescopes are cheap and offer a great 'bang for buck'  if you do not mind star spikes. Otherwise A 6"- 8" sct with reducer works fine and gives you some versatility with focal length.

You will also need a laptop for sharpcap unless you plan to use something like an Asiair, there is a thread on laptops here also in the EAA forums. Have a play around with astronomy tools so you get an idea of different scopes and camera combo's field of view on DSO's

 

https://astronomy.to.../field_of_view/

 

There is no right or wrong answers, it is about budget and expectations. With your budget you should be able to get a good setup going. I would also advise on looking at the EAA image gallery to see what different combo cameras and scopes are capable of. Good luck and weather in your EAA adventure laugh.gif


Edited by Barkingsteve, 09 February 2021 - 05:42 PM.


#6 alphatripleplus

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Posted 09 February 2021 - 05:47 PM

I see a lot of recommendations above for the 533MC, but if the OP wants to try one of two smaller and cheaper cameras he explicitly mentions, I would suggest the 224MC. I started EAA with that camera, and it is a good camera to learn on, without making as large a financial commitment as something like the 533MC. You can also construct a dark library with a non-cooled camera like the 224MC (as I do) indexed by termperature, exposure and gain.

 

Of course, if the OP  is comfortable jumping in with a larger sensor cooled camera, that is a fine way to start too.


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#7 Ptarmigan

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Posted 09 February 2021 - 07:15 PM

224 or 385 sensors are great to start with. I have used Revolution Imager R2 and Altair GPCAM3 385C.

 

I am pleased with both of them. cool.gif waytogo.gif



#8 GoFish

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Posted 09 February 2021 - 08:44 PM

I, too, started with an R2. Quickly followed by a 224MC. 

 

It is very challenging to “put an object on the sensor” of those cameras. The field of view is tiny. Unless you have somehow created a very good pointing model with your GoTo mount, it can be frustrating to find what you wish to observe. And don’t even get me started about the chicken-and-egg problem of needing to be focused to see an(y) object, but not being able to adjust focus until you have found an object!

 

My opinion is that a large sensor camera is well worth the added expense for all but the most tightly constrained budgets. 

 

OTOH, if camera cost is a potential deal killer, then a 224MC can be a good choice, provided a suitably short (say 400mm max) focal length scope is used. 


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#9 astrohamp

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Posted 09 February 2021 - 10:58 PM

Outfitting your observing system with a GoTo mount controllable by computer will allow 'remote' or indoor observations.  More portable instruments will ease the burden of lugging them around, whether to backyard or more dark sites.  Confining your set up to 12v DC operation makes for ease of deployment on batteries. 

A refractor of 80-110mm diameter makes for ease of use, transport, and has shown to be very effective for both EAA observing and astro photography. Some good reviews can be found in these forums.  The smaller refractor allows one to consider lower payload mounts from say iOptron.  I can only speak for the observatory class CEM120 which I have taken to the field for months of observing since its purchase.  New or used there may be issues with obtaining your choices due to circumstances.

Battery operation is mandatory for off-grid (remote dark site) observing requiring the choice between LifePo4 lithium or lead AGM/SLA batteries.  Here, knowing observing time and instrument load is important for deciding how big to go.  'All' my set up is directly 12v DC powerable.  Mount, dew control, cameras, focuser, astro computer, laptop computer, even two of the three monitors I use.  The 4k monitor must have a 12v to 19v DC boost converter to supply 19 volts.  I do not use an AC inverter due to efficiency losses.  My sessions can easily last 8 hours pushing my battery into the reduced life zone, a calculated compromise.

Then for observing convenience one implements a scope mounted computer and links it to a second one inside a warm/cool space.  Some do by wire, I use wireless and Windows Remote Desktop or similar link software,  This allows control room set up computer/monitor/TV to view (control) what is imaging outside via indoor laptop/desktop computer.  At home my back yard AC powered instruments are remotely controlled with a desk top computer while viewing one or two 4k UHD monitor/TVs.  In field I set up a 'dark shed' (tent) to house laptop, monitor(s), table, swivel chair etc.  Advantage is near zero light pollution for fellow visual observers, dew control, and keeps bugs at bay when in season.  Fans required in summer (also 12v powered).

SharpCap Pro image capture/control software can be your best instrument interface, although others may recommend differently.  I keep my eyepiece cases ready to go but these days I am able to see so many more objects in the night sky via EAA, even ones that look similar to averted vision but displayed on a computer monitor.  The EAA benefit is these new objects are orders of magnitude fainter then any of my eyepiece views with the same telescope.  All this with a 152mm achromat OTA. 

Good luck on your journey.



 


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#10 dcweaver

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Posted 10 February 2021 - 02:36 AM

I just got started with EAA myself.  I did it with borrowed equipment, so I didn't have much choice regarding what I started with.  Needless to say it was hard.  If I had a do-over and was buying equipment from scratch, this is what I would do.

   
Hardware
Celestron Nexstar Evolution 8 ($1700)
Starizona Night Owl 0.4x focal reducer ($300)
ZWO ASI183MC color camera ($550)
Zwo T-thread spacer - 21mm ($18)
Celestron StarSense ($390)
Astrozap dew heater ($52)
Astrozap heater cigarette plug cable ($41)
RS-232 cable ($19)
USB to RS-232 converter cable ($23)

   
Software
SharpCap Pro ($15/year)
CPWI (free)

   
Total = $3108

   

Celestron makes hardware and software that work well together to minimize the "fiddle factor".  This lets you spend more time observing and less time tweaking.  I also like the versatility of the Schmidt Cassegrain (SCT) optics.  An 8 inch SCT has enough aperture to keep you busy for many years.  It is good for both planets and deep sky.  Their alt-az mounts are easy to work with and produce good EAA results for members on the forum.

   
The focal reducer is essential.  I can't emphasize that enough.  It increases the field of view, so you can see where you are relative to reference stars, and it increases the speed of the optics to help the "film" develop faster.  Everything gets easier with shorter focal lengths and faster f/ratio.  The challenge with scopes that naturally have short focal lengths and fast optics, like a refractor or a Newtonian, is they are either very small and expensive (APO Refractor) or they are very big and heavy (Newtonian).  Big scopes require big expensive mounts to keep them steady.

   
Bigger camera sensors also improve the field of view.  I recommend a ZWO camera.  I have one, and it has been very "turnkey" for me.  You want a sensor big enough to frame the full Moon when using the reducer.  That's enough field of view to put objects on the sensor reliably with any of Celestron's goto mounts.  A ZWO ASI183 will do this with the Night Owl reducer, and it has smaller pixels for better resolution allowing you to zoom in on the computer more before things look blocky and pixelated.  The T-thread spacer on the list places the camera at the correct distance from the reducer.  The online tool at the following link will help you experiment with different scope, reducer, and camera combinations.  Don't get sucked into the huge targets like the North American Nebula or Andromeda Galaxy.  For every one of those, there are many more small to medium sized targets that are just as interesting, if not more interesting.

   
https://astronomy.to.../field_of_view/

   

Take advantage of technology to make life easier.  Especially if your wife has impaired vision.  Celestron's StarSense alignment camera will make alignment much easier than trying to center stars in a finder, eyepiece, or crosshairs on a computer screen.   It also has the ability to correct the position of the scope if you are slightly off target after a goto (StarSense Help button).  Since you need a computer to run the camera, you might as well take advantage of their CPWI software.  It replaces the clunky hand controller, gives you a sky map to find objects, and it works with StarSense.  For image capture and live stacking, I only know SharpCap, but it fits the "turnkey" theme.  It was very easy to get working once I had a focal reducer.

   
A dew heater for the scope is another must.  You may even want one for the StarSense and ASI183.  That caught me by surprise.  I don't use the controller, but if you have three heaters, you might want it. The adapter cable with the cigarette lighter plug is the minimum needed for 1 or 2 heaters.

   
How you power everything depends on where you want to use the scope.  At home, I prefer AC power with AC/DC converter bricks (e.g. like a laptop power cord).  If you want to use the scope away from home, you will need batteries.  The Evolution has a built in battery, but you may need another battery for the dew heater (I didn't include that in the list).  I don't think the USB power port on the EVO has enough capacity to power the heater.

   

For the money, this is a very capable EAA system that is as "turnkey" and "easy" as I can find.  Throw in 4K UHD computer graphics and monitors (or a TV) and you are ready to use everything the high res ASI183 can deliver.

   

Best of luck whichever way you go!


Edited by dcweaver, 10 February 2021 - 02:44 AM.

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#11 dcweaver

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Posted 10 February 2021 - 02:46 AM

One last thing.  Get a Bahtinov mask to help focus.  AgenaAstro makes some inexpensive ones.  They make life much easier as well.


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#12 tomb1

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Posted 10 February 2021 - 03:29 AM

It sounds like you're looking for an EAA setup that is true to the name being that you're striving to make visual astronomy accessible for your wife. Kudos - good husband, I'd like to offer the benefit of about four years of my experience on the subject.  My goal from the start has been to achieve an experience as close as possible to looking through an eyepiece.  A good part of this experience is relative simplicity.  EAA setups can easily approach the complexity of an astrophotography rig.    There are fully integrated instruments like the Vaonis Stellina or Unistellar.  Maybe not technically the best solution, but definitely the simplest.  

 

If you want as close to real-time images you will need aperture.  4" is minimal.  I find that a 6" F4 Newt (GSO/TPO/Apertura/Orion) is a convenient size that allows 15 to 30 second exposures of deep sky objects.  More aperture DOES have the same advantages as with visual.  In this case more aperture = shorter exposure time = good.  Keep in mind though that if you only have one camera and one telescope, then you only have one field of view.  My 6" F4 is great for most large objects (Andromeda Galaxy, Orion/Horsehead/Lagoon/Eagle/North America nebulas, Pleiades, etc).  Many galaxies will want more magnification.

 

I used Sharpcap for three years.  It's very capable, cheap (only consider the pro version), and works with most cameras.  Unfortunately, its user interface is rather dated and it's limited to Windows machines so you're stuck using a laptop.

 

Describing my present configuration is going to make me sound like a ZWO commercial. ZWO hardware is a closed universe kind of like Apple.  If you don't mind that scenario then the relative simplicity of having a fully integrated system can be had by using the ASIAir Pro (Raspberry Pi4 based) as the computer, a ZWO camera such as the ASI294MC (12Mpixel), and possibly a ZWO electronic focuser.  This is the setup I use.  The advantages are that a tablet is used as the user interface and the ASIAir software controls everything including the mount.  

 

I'm finding that this setup has several convenience advantages over a wired USB/RS232 laptop setup.  Since the ASIAir is mounted on the telescope, wired connections are made to all of the hardware including the mount.  The wireless connection to the tablet can lose connection without affecting operation of the system.  Most importantly, the mount won't lose its mind and forget where its at. (bad - so bad)  The ASIair can be configured to generate its own network or to exist on another such as your home wi-fi network so you can sit in front of your fireplace and observe when its cold outside.

 

I find that using a tablet (iPad in my case) makes for a much more pleasurable observing experience over a laptop.  BTW, multiple tablets can connect the ASIAir Pro simultaneously and tablet to TV video wireless interfaces are common.  

 

Hope this helps.    


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#13 alphatripleplus

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Posted 10 February 2021 - 09:01 AM

I, too, started with an R2. Quickly followed by a 224MC. 

 

It is very challenging to “put an object on the sensor” of those cameras. The field of view is tiny. Unless you have somehow created a very good pointing model with your GoTo mount, it can be frustrating to find what you wish to observe. And don’t even get me started about the chicken-and-egg problem of needing to be focused to see an(y) object, but not being able to adjust focus until you have found an object!

 

My opinion is that a large sensor camera is well worth the added expense for all but the most tightly constrained budgets. 

 

OTOH, if camera cost is a potential deal killer, then a 224MC can be a good choice, provided a suitably short (say 400mm max) focal length scope is used. 

If you have a plate solving application running, it is very simple using a small sensor camera to find and centre targets in literally one click using a plate solver linked to your mount and camera capture software. I use ASTAP for plate solving with Cartes du Ciel planetarium software to control the mount, and usually SharpCap for capture. The time savings that using a plate solve bring make it one of the best things to incorporate in your EAA tool kit in my opinion, particularly if you are struggling to get targets in the camera's field of view.


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#14 Bill05

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Posted 10 February 2021 - 11:16 AM

I apologize for appearing to ignore your answers to my post.  After reading each post I do a lot of searching and reading to understand the information  you are graciously providing. I am still trying to wrap my mind around about the magnitude of information, then explain to my wife so she can understand it enough to help with the decisions. She thinks at least a basic understanding is better than just accepting an answer. We both are grateful for your assistance so far.

We are going with a bigger camera, cooled. she is still undecided about a 6 or 8 inch Newt. I am looking into the how and why of focal reducers.  She still likes the bigger aperture for me and the grand kids to look thru, she wants them to see things, not the TV, or tablet.



#15 Bill05

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Posted 10 February 2021 - 01:36 PM

The wife is still considering an 8" newt, F/L 1000mm and F/R f/4.9 or a 6" newt.  F/L 750mm and F/R f/5. Since

From what I am finding, a focal reducer is not used on a newt. yes, no, maybe? It may have been suggested for another type of scope.

The other Item I am unsure about are filters. are they needed, or optional in Bortle 5? if needed, which ones to start with?



#16 dcweaver

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Posted 10 February 2021 - 11:53 PM

Bill, that is correct.  A focal reducer is not recommended with a Newt.  It is already relatively fast at f/4.9 and a focal reducer will make the existing aberrations, like coma, worse.  In fact, with a big sensor, you may need a coma corrector, so the stars at the edge of the field don't look like little comets.

   
Here are a few things to look for in a Newtonian.

   
1) Get an "Astrograph".  They have a secondary mirror that is closer to the primary.  This places the focal point further outside the tube from the secondary.  With a non-Astrograph, the focal point is not very far outside the main tube, and you may not be able to reach focus with the focuser wound in as far as it will go.  This may be more of a problem with DSLR cameras that require 55 mm of backfocus, but it doesn't hurt to get an Astrograph as an insurance policy.  Orion Telescope and Binocular has good examples of 6 and 8 inch models.  All of the dealers sell re-branded versions of the same Newts from GSO (manufacturer) with small tweaks.  The Orion version has a steel reinforcing plate inside the tube where the focuser mounts to keep it rigid with camera equipment attached.

   
2) If you get a 6 inch, you may need a longer vixen rail to balance the Astrograph on an EQ mount.  This depends on how much weight you add up front (camera, filters, finder, Barlow, etc).  You won't know you have this problem until you have the equipment.  A longer rail will let you place the rings at the front and back of the scope, giving you more rail to work with to find a good balance point.

   
3) You may need to collimate often, so some "Bob's Knobs" might be helpful.  Newtonian owners collimate frequently.  I don't know what drives that, but SCT owners don't seem to do it as often.  I don't collimate my Maksutov Cassegrain at all.  In a visually impaired situation, achieving good collimation may be a challenge.  If the impairment is severe, you might be better off with a refractor that doesn't need collimation unless it gets dropped or jarred really hard.

   
4) Again, let technology work for you.  SharpCap or a Polemaster will make polar alignment much easier.  Polar alignment is hard otherwise.  It requires gymnastics to look through a polar scope, and a polar scope may be problematic with impaired vision.  I've never done a drift alignment, but the process described in various documents was not trivial.

   
Oddly enough, the Orion 6" Astrograph with an Orion Sirius EQ-G mount was at the top of my list for a while.  The thing that stopped me from moving forward was that every time I was ready to pull the trigger, I found another little gotcha that required a workaround.  I also wanted something that would provide more detail on the planets, which are some of my favorite objects.

   
I fully understand where your wife is coming from not wanting the grandkids to see life through a computer screen.  I often feel the same way.  Unfortunately, the camera was the only way I could see anything at all.  When I looked through my eyepiece, I couldn't see anything but grey smudges.  My wife, who has hawk eyes, started a running joke about how nice each particular smudge was, and how each one was so different than the last one.  Knowing the attention span of kids, I don't think a smudge will hold their attention for long, but you may have better luck in the dark skies above the old Reynolds / Alcoa smelter.

 

Here's a recent post illustrating how expectations can spell the difference between enthusiasm and apathy:

   

https://www.cloudyni...he-grey-smudge/


Edited by dcweaver, 10 February 2021 - 11:57 PM.

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#17 Bill05

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Posted 11 February 2021 - 08:10 AM

great story and picture.  The wife was thinking along hubble results but she likes what others are posting and understands the difference now. thanks for the advice, I look into all advise and discuss it with her.  part of the reason for long times between responses.



#18 alphatripleplus

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Posted 11 February 2021 - 08:58 AM

One thing to keep in mind is that it might be "educational" to show the kids the difference in what you can see through an eyepiece with the same telescope vs camera and laptop on the same target. I say educational, because it will lead to questions about how the camera/laptop view can remove the sky background, and why live stacking improves the view with time.  Depending on the age of your kids, learning about the "how" this all works could spark some interest - more so than just looking at a pretty picture.smile.gif


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#19 GoFish

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Posted 11 February 2021 - 05:25 PM

If you have a plate solving application running, it is very simple using a small sensor camera to find and centre targets in literally one click using a plate solver linked to your mount and camera capture software. I use ASTAP for plate solving with Cartes du Ciel planetarium software to control the mount, and usually SharpCap for capture. The time savings that using a plate solve bring make it one of the best things to incorporate in your EAA tool kit in my opinion, particularly if you are struggling to get targets in the camera's field of view.

Yes, I agree.

 

But even plate solving improves with a larger sensor, presumably because there are so many more stars in the image.

 

My first efforts at platesolving was using a 224MC. I experienced a fair number of “did not solve” outcomes with the small sensor. I have rarely experienced a DNS with the 294 sensor. 


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#20 GoFish

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Posted 11 February 2021 - 05:38 PM

Regarding the (good) advice to look at astrograhs, be aware that most of them are f/4.

 

In my experience, collimating a Newt at f/4 is an order of magnitude more challenging, and more necessary, than f/5.  If you don’t mind picking up a good barlowed laser, or cheshire/autocollimator kit, for your f/4 then you will be fine. 

 

And, for me, the coma (comet-looking stars around the perimeter) at f/5 is tolerable. At f/4, it is not OK for me without a coma corrector. (I must be an f/5 Newt kinda guy since I own and really like 3 of them.)

 

I can vouch for the stock focuser on the OMNI XLT 150 Newt having adequate travel for an ASI294MC Pro camera, just FWIW. The OMNI 150 is not an astrograph. I miss having a 2-speed focuser, but I can get by without it. 


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#21 alphatripleplus

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Posted 11 February 2021 - 06:13 PM

I should add that I have been very surprised that ASTAP works very reliably as a plate solver with my tiny ASI290MM sensor (about the same size of the ASI224MC) even at 1,000mm focal length; the field of view is only something like 19' x 11'. So if you do try plate solving with a small sensor camera, you may find that not all solvers are equally reliable.



#22 Bill05

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Posted 11 February 2021 - 06:43 PM

a laser collimator has been on the list since my wife wanted a 12" Dob.  A coma corrector is on a list of "do I need this". I just do not know enough yet.  So much to learn about, most of it will be after the scope and camera arrive.  I think I am learning things, I am able to explain some of this to my wife so she can help with the decisions. The best of it is she is encouraging, understandable and laughs at me.



#23 tomb1

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Posted 13 February 2021 - 10:11 PM

The wife is still considering an 8" newt, F/L 1000mm and F/R f/4.9 or a 6" newt.  F/L 750mm and F/R f/5. Since

From what I am finding, a focal reducer is not used on a newt. yes, no, maybe? It may have been suggested for another type of scope.

The other Item I am unsure about are filters. are they needed, or optional in Bortle 5? if needed, which ones to start with?

Bill,

If you're undecided about the telescope and what focal length to use and with what camera, it might be helpful to use a program like Sky Safari (Stellarium may do this as well).  This planetarium program has a facility for generating a field of view indicator for telescope/camera combinations.  Basically you get a rectangle on the star field that shows you how big any particular dark-sky object will appear on your video screen.  (Does the same with telescope/eyepiece combinations.)  I used this method to determine that a 6" F4 telescope would show the entire Andromeda Galaxy using my ASI294MC camera.  All the information you need is the focal length of the telescope and the sensor size for the camera.  You can do all the combinations you want and display them simultaneously.  Takes out the guess-work.



#24 alphatripleplus

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Posted 14 February 2021 - 08:46 AM

 

The other Item I am unsure about are filters. are they needed, or optional in Bortle 5? if needed, which ones to start with?

I have roughly Bortle 4 skies and don't use filters most of the time, except  for a narrowband H-alpha filter for emission nebulae with a mono camera. A UV/IR may help with a refractor to tighten up stars a little, but if you have a Newt you shouldn't have any chromatic aberration resulting in star bloat.



#25 Bill05

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Posted 14 February 2021 - 09:52 PM

Bill,

If you're undecided about the telescope and what focal length to use and with what camera, it might be helpful to use a program like Sky Safari (Stellarium may do this as well).  This planetarium program has a facility for generating a field of view indicator for telescope/camera combinations.  Basically you get a rectangle on the star field that shows you how big any particular dark-sky object will appear on your video screen.  (Does the same with telescope/eyepiece combinations.)  I used this method to determine that a 6" F4 telescope would show the entire Andromeda Galaxy using my ASI294MC camera.  All the information you need is the focal length of the telescope and the sensor size for the camera.  You can do all the combinations you want and display them simultaneously.  Takes out the guess-work.

Do I need to use a specific Sky Safari app or will any of them work?  There are several different apps.




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