Every beginning astronomer should have some idea of the visual limits of his/her telescope. For example, why search for 14th magnitude Pluto if you only have a 70 mm scope (which simply can't go that deep) and/or you are observing under light polluted skies? On the other hand, my Celestron CPC 800 (8" SCT) under Bortle Class 2 skies can go much deeper…my record is magnitude 15.4 stars (see Wikipedia or search Google for "Bortle Scale).
The Telescope Visual Limiting Magnitude (TVLM) is affected by telescope aperture, seeing conditions, the observer, and several other factors. It is not possible to calculate a definitive TVLM, but it is possible to estimate it for your conditions with a simple formula. Actually, there are several formulas floating around out there.
If you would like more information about TVLM, and don't mind some simple math, I refer you to the following resources I recently created and posted online. These resources cover five formulas for estimating TVLM: three that are based only on the telescope aperture and two others that include additional parameters. The first resource is a PTC Mathcad worksheetfor TVLM that I posted at http://communities.ptc.com/docs/DOC-5277 . Mathcad is mathematics software that is targeted primarily at engineers and scientists who need to see the math, not just the results (Excel, for example, shows only a table of data and results; the formulas aren't normally shown and when you flip to formula view, the formulas are formatted more like FORTRAN code than textbook-style equations). Since Mathcad is a niche product and I don't expect very many non-engineers to have a copy, the .zip file I posted there also includes an Adobe Acrobat .pdf file that you can read for information on the various methods used to estimate the TVLM. If your math background extends at least to Algebra I, you should be able to figure it out. But, ask me for help if you can't
Secondly, last Saturday, I gave a presentation on TVLM for my astronomy club. I converted my PowerPoint presentation to .jpgs and posted them as a public album on Facebook. You can access it with or without being a member of Facebook at https://www.facebook.com/media/set/?set=a.10205329095573313.1073741856.1425866703&type=1&l=9730d636f9 . There is also a video version (with no sound) of the presentation at https://www.facebook.com/video.php?v=10205336473997769&set=vb.1425866703&type=3&theater .
The Telescope Visual Limiting Magnitude (TVLM) is affected by telescope aperture, seeing conditions, the observer, and several other factors. It is not possible to calculate a definitive TVLM, but it is possible to estimate it for your conditions with a simple formula. Actually, there are several formulas floating around out there.
If you would like more information about TVLM, and don't mind some simple math, I refer you to the following resources I recently created and posted online. These resources cover five formulas for estimating TVLM: three that are based only on the telescope aperture and two others that include additional parameters. The first resource is a PTC Mathcad worksheetfor TVLM that I posted at http://communities.ptc.com/docs/DOC-5277 . Mathcad is mathematics software that is targeted primarily at engineers and scientists who need to see the math, not just the results (Excel, for example, shows only a table of data and results; the formulas aren't normally shown and when you flip to formula view, the formulas are formatted more like FORTRAN code than textbook-style equations). Since Mathcad is a niche product and I don't expect very many non-engineers to have a copy, the .zip file I posted there also includes an Adobe Acrobat .pdf file that you can read for information on the various methods used to estimate the TVLM. If your math background extends at least to Algebra I, you should be able to figure it out. But, ask me for help if you can't
Secondly, last Saturday, I gave a presentation on TVLM for my astronomy club. I converted my PowerPoint presentation to .jpgs and posted them as a public album on Facebook. You can access it with or without being a member of Facebook at https://www.facebook.com/media/set/?set=a.10205329095573313.1073741856.1425866703&type=1&l=9730d636f9 . There is also a video version (with no sound) of the presentation at https://www.facebook.com/video.php?v=10205336473997769&set=vb.1425866703&type=3&theater .
